[PATCH net-next V2 0/8] Packed virtqueue support for vhost

STALE2858d

Revision v2 of 3 in this series.

25 messages, 5 authors, 2018-10-18 · open the first message on its own page

[PATCH net-next V2 0/8] Packed virtqueue support for vhost

From: Jason Wang <hidden>
Date: 2018-07-16 03:28:28 

Hi all:

This series implements packed virtqueues. The code were tested with
Tiwei's guest driver series at https://patchwork.ozlabs.org/cover/942297/


Pktgen test for both RX and TX does not show obvious difference with
split virtqueues. The main bottleneck is the guest Linux driver, since
it can not stress vhost for a 100% CPU utilization. A full TCP
benchmark is ongoing. Will test virtio-net pmd as well when it was
ready.

Notes:
- This version depends on Tiwei's series at https://patchwork.ozlabs.org/cover/942297/

This version were tested with:

- Zerocopy (Out of Order) support
- vIOMMU support
- mergeable buffer on/off
- busy polling on/off
- vsock (nc-vsock)

Changes from V1:
- drop uapi patch and use Tiwei's
- split the enablement of packed virtqueue into a separate patch

Changes from RFC V5:

- save unnecessary barriers during vhost_add_used_packed_n()
- more compact math for event idx
- fix failure of SET_VRING_BASE when avail_wrap_counter is true
- fix not copy avail_wrap_counter during GET_VRING_BASE
- introduce SET_VRING_USED_BASE/GET_VRING_USED_BASE for syncing last_used_idx
- rename used_wrap_counter to last_used_wrap_counter
- rebase to net-next

Changes from RFC V4:

- fix signalled_used index recording
- track avail index correctly
- various minor fixes

Changes from RFC V3:

- Fix math on event idx checking
- Sync last avail wrap counter through GET/SET_VRING_BASE
- remove desc_event prefix in the driver/device structure

Changes from RFC V2:

- do not use & in checking desc_event_flags
- off should be most significant bit
- remove the workaround of mergeable buffer for dpdk prototype
- id should be in the last descriptor in the chain
- keep _F_WRITE for write descriptor when adding used
- device flags updating should use ADDR_USED type
- return error on unexpected unavail descriptor in a chain
- return false in vhost_ve_avail_empty is descriptor is available
- track last seen avail_wrap_counter
- correctly examine available descriptor in get_indirect_packed()
- vhost_idx_diff should return u16 instead of bool

Changes from RFC V1:

- Refactor vhost used elem code to avoid open coding on used elem
- Event suppression support (compile test only).
- Indirect descriptor support (compile test only).
- Zerocopy support.
- vIOMMU support.
- SCSI/VSOCK support (compile test only).
- Fix several bugs

Jason Wang (8):
  vhost: move get_rx_bufs to vhost.c
  vhost: hide used ring layout from device
  vhost: do not use vring_used_elem
  vhost_net: do not explicitly manipulate vhost_used_elem
  vhost: vhost_put_user() can accept metadata type
  vhost: packed ring support
  vhost: event suppression for packed ring
  vhost: enable packed virtqueues

 drivers/vhost/net.c        | 143 ++-----
 drivers/vhost/scsi.c       |  62 +--
 drivers/vhost/vhost.c      | 994 ++++++++++++++++++++++++++++++++++++++++-----
 drivers/vhost/vhost.h      |  55 ++-
 drivers/vhost/vsock.c      |  42 +-
 include/uapi/linux/vhost.h |   7 +
 6 files changed, 1035 insertions(+), 268 deletions(-)

-- 
2.7.4

[PATCH net-next V2 1/8] vhost: move get_rx_bufs to vhost.c

From: Jason Wang <hidden>
Date: 2018-07-16 03:28:34 

Move get_rx_bufs() to vhost.c and rename it to
vhost_get_bufs(). This helps to hide vring internal layout from
specific device implementation. Packed ring implementation will
benefit from this.

Signed-off-by: Jason Wang <redacted>
---
 drivers/vhost/net.c   | 83 ++-------------------------------------------------
 drivers/vhost/vhost.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++
 drivers/vhost/vhost.h |  7 +++++
 3 files changed, 88 insertions(+), 80 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index b224036..03dd1de 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -702,83 +702,6 @@ static int vhost_net_rx_peek_head_len(struct vhost_net *net, struct sock *sk,
 	return len;
 }
 
-/* This is a multi-buffer version of vhost_get_desc, that works if
- *	vq has read descriptors only.
- * @vq		- the relevant virtqueue
- * @datalen	- data length we'll be reading
- * @iovcount	- returned count of io vectors we fill
- * @log		- vhost log
- * @log_num	- log offset
- * @quota       - headcount quota, 1 for big buffer
- *	returns number of buffer heads allocated, negative on error
- */
-static int get_rx_bufs(struct vhost_virtqueue *vq,
-		       struct vring_used_elem *heads,
-		       int datalen,
-		       unsigned *iovcount,
-		       struct vhost_log *log,
-		       unsigned *log_num,
-		       unsigned int quota)
-{
-	unsigned int out, in;
-	int seg = 0;
-	int headcount = 0;
-	unsigned d;
-	int r, nlogs = 0;
-	/* len is always initialized before use since we are always called with
-	 * datalen > 0.
-	 */
-	u32 uninitialized_var(len);
-
-	while (datalen > 0 && headcount < quota) {
-		if (unlikely(seg >= UIO_MAXIOV)) {
-			r = -ENOBUFS;
-			goto err;
-		}
-		r = vhost_get_vq_desc(vq, vq->iov + seg,
-				      ARRAY_SIZE(vq->iov) - seg, &out,
-				      &in, log, log_num);
-		if (unlikely(r < 0))
-			goto err;
-
-		d = r;
-		if (d == vq->num) {
-			r = 0;
-			goto err;
-		}
-		if (unlikely(out || in <= 0)) {
-			vq_err(vq, "unexpected descriptor format for RX: "
-				"out %d, in %d\n", out, in);
-			r = -EINVAL;
-			goto err;
-		}
-		if (unlikely(log)) {
-			nlogs += *log_num;
-			log += *log_num;
-		}
-		heads[headcount].id = cpu_to_vhost32(vq, d);
-		len = iov_length(vq->iov + seg, in);
-		heads[headcount].len = cpu_to_vhost32(vq, len);
-		datalen -= len;
-		++headcount;
-		seg += in;
-	}
-	heads[headcount - 1].len = cpu_to_vhost32(vq, len + datalen);
-	*iovcount = seg;
-	if (unlikely(log))
-		*log_num = nlogs;
-
-	/* Detect overrun */
-	if (unlikely(datalen > 0)) {
-		r = UIO_MAXIOV + 1;
-		goto err;
-	}
-	return headcount;
-err:
-	vhost_discard_vq_desc(vq, headcount);
-	return r;
-}
-
 /* Expects to be always run from workqueue - which acts as
  * read-size critical section for our kind of RCU. */
 static void handle_rx(struct vhost_net *net)
@@ -831,9 +754,9 @@ static void handle_rx(struct vhost_net *net)
 						      &busyloop_intr))) {
 		sock_len += sock_hlen;
 		vhost_len = sock_len + vhost_hlen;
-		headcount = get_rx_bufs(vq, vq->heads + nvq->done_idx,
-					vhost_len, &in, vq_log, &log,
-					likely(mergeable) ? UIO_MAXIOV : 1);
+		headcount = vhost_get_bufs(vq, vq->heads + nvq->done_idx,
+					   vhost_len, &in, vq_log, &log,
+					   likely(mergeable) ? UIO_MAXIOV : 1);
 		/* On error, stop handling until the next kick. */
 		if (unlikely(headcount < 0))
 			goto out;
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index a502f1a..8814e5b 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2104,6 +2104,84 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 }
 EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
 
+/* This is a multi-buffer version of vhost_get_desc, that works if
+ *	vq has read descriptors only.
+ * @vq		- the relevant virtqueue
+ * @datalen	- data length we'll be reading
+ * @iovcount	- returned count of io vectors we fill
+ * @log		- vhost log
+ * @log_num	- log offset
+ * @quota       - headcount quota, 1 for big buffer
+ *	returns number of buffer heads allocated, negative on error
+ */
+int vhost_get_bufs(struct vhost_virtqueue *vq,
+		   struct vring_used_elem *heads,
+		   int datalen,
+		   unsigned *iovcount,
+		   struct vhost_log *log,
+		   unsigned *log_num,
+		   unsigned int quota)
+{
+	unsigned int out, in;
+	int seg = 0;
+	int headcount = 0;
+	unsigned d;
+	int r, nlogs = 0;
+	/* len is always initialized before use since we are always called with
+	 * datalen > 0.
+	 */
+	u32 uninitialized_var(len);
+
+	while (datalen > 0 && headcount < quota) {
+		if (unlikely(seg >= UIO_MAXIOV)) {
+			r = -ENOBUFS;
+			goto err;
+		}
+		r = vhost_get_vq_desc(vq, vq->iov + seg,
+				      ARRAY_SIZE(vq->iov) - seg, &out,
+				      &in, log, log_num);
+		if (unlikely(r < 0))
+			goto err;
+
+		d = r;
+		if (d == vq->num) {
+			r = 0;
+			goto err;
+		}
+		if (unlikely(out || in <= 0)) {
+			vq_err(vq, "unexpected descriptor format for RX: "
+				"out %d, in %d\n", out, in);
+			r = -EINVAL;
+			goto err;
+		}
+		if (unlikely(log)) {
+			nlogs += *log_num;
+			log += *log_num;
+		}
+		heads[headcount].id = cpu_to_vhost32(vq, d);
+		len = iov_length(vq->iov + seg, in);
+		heads[headcount].len = cpu_to_vhost32(vq, len);
+		datalen -= len;
+		++headcount;
+		seg += in;
+	}
+	heads[headcount - 1].len = cpu_to_vhost32(vq, len + datalen);
+	*iovcount = seg;
+	if (unlikely(log))
+		*log_num = nlogs;
+
+	/* Detect overrun */
+	if (unlikely(datalen > 0)) {
+		r = UIO_MAXIOV + 1;
+		goto err;
+	}
+	return headcount;
+err:
+	vhost_discard_vq_desc(vq, headcount);
+	return r;
+}
+EXPORT_SYMBOL_GPL(vhost_get_bufs);
+
 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
 {
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 6c844b9..52edd242 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -185,6 +185,13 @@ int vhost_get_vq_desc(struct vhost_virtqueue *,
 		      struct iovec iov[], unsigned int iov_count,
 		      unsigned int *out_num, unsigned int *in_num,
 		      struct vhost_log *log, unsigned int *log_num);
+int vhost_get_bufs(struct vhost_virtqueue *vq,
+		   struct vring_used_elem *heads,
+		   int datalen,
+		   unsigned *iovcount,
+		   struct vhost_log *log,
+		   unsigned *log_num,
+		   unsigned int quota);
 void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
 
 int vhost_vq_init_access(struct vhost_virtqueue *);
-- 
2.7.4

[PATCH net-next V2 2/8] vhost: hide used ring layout from device

From: Jason Wang <hidden>
Date: 2018-07-16 03:28:38 

We used to return descriptor head by vhost_get_vq_desc() to device and
pass it back to vhost_add_used() and its friends. This exposes the
internal used ring layout to device which makes it hard to be extended for
e.g packed ring layout.

So this patch tries to hide the used ring layout by

- letting vhost_get_vq_desc() return pointer to struct vring_used_elem
- accepting pointer to struct vring_used_elem in vhost_add_used() and
  vhost_add_used_and_signal()

This could help to hide used ring layout and make it easier to
implement packed ring on top.

Signed-off-by: Jason Wang <redacted>
---
 drivers/vhost/net.c   | 48 +++++++++++++++++++++------------------
 drivers/vhost/scsi.c  | 62 +++++++++++++++++++++++++++------------------------
 drivers/vhost/vhost.c | 52 +++++++++++++++++++++---------------------
 drivers/vhost/vhost.h |  9 +++++---
 drivers/vhost/vsock.c | 42 +++++++++++++++++-----------------
 5 files changed, 113 insertions(+), 100 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 03dd1de..a8c9506 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -430,15 +430,16 @@ static int vhost_net_enable_vq(struct vhost_net *n,
 
 static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
 				    struct vhost_virtqueue *vq,
+				    struct vring_used_elem *used_elem,
 				    struct iovec iov[], unsigned int iov_size,
 				    unsigned int *out_num, unsigned int *in_num,
 				    bool *busyloop_intr)
 {
 	unsigned long uninitialized_var(endtime);
-	int r = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
+	int r = vhost_get_vq_desc(vq, used_elem, vq->iov, ARRAY_SIZE(vq->iov),
 				  out_num, in_num, NULL, NULL);
 
-	if (r == vq->num && vq->busyloop_timeout) {
+	if (r == -ENOSPC && vq->busyloop_timeout) {
 		preempt_disable();
 		endtime = busy_clock() + vq->busyloop_timeout;
 		while (vhost_can_busy_poll(endtime)) {
@@ -451,8 +452,9 @@ static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
 			cpu_relax();
 		}
 		preempt_enable();
-		r = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
-				      out_num, in_num, NULL, NULL);
+		r = vhost_get_vq_desc(vq, used_elem, vq->iov,
+				      ARRAY_SIZE(vq->iov), out_num, in_num,
+				      NULL, NULL);
 	}
 
 	return r;
@@ -474,7 +476,6 @@ static void handle_tx(struct vhost_net *net)
 	struct vhost_net_virtqueue *nvq = &net->vqs[VHOST_NET_VQ_TX];
 	struct vhost_virtqueue *vq = &nvq->vq;
 	unsigned out, in;
-	int head;
 	struct msghdr msg = {
 		.msg_name = NULL,
 		.msg_namelen = 0,
@@ -487,6 +488,7 @@ static void handle_tx(struct vhost_net *net)
 	size_t hdr_size;
 	struct socket *sock;
 	struct vhost_net_ubuf_ref *uninitialized_var(ubufs);
+	struct vring_used_elem used;
 	bool zcopy, zcopy_used;
 	int sent_pkts = 0;
 
@@ -512,14 +514,11 @@ static void handle_tx(struct vhost_net *net)
 			vhost_zerocopy_signal_used(net, vq);
 
 		busyloop_intr = false;
-		head = vhost_net_tx_get_vq_desc(net, vq, vq->iov,
-						ARRAY_SIZE(vq->iov),
-						&out, &in, &busyloop_intr);
-		/* On error, stop handling until the next kick. */
-		if (unlikely(head < 0))
-			break;
+		err = vhost_net_tx_get_vq_desc(net, vq, &used, vq->iov,
+					       ARRAY_SIZE(vq->iov),
+					       &out, &in, &busyloop_intr);
 		/* Nothing new?  Wait for eventfd to tell us they refilled. */
-		if (head == vq->num) {
+		if (err == -ENOSPC) {
 			if (unlikely(busyloop_intr)) {
 				vhost_poll_queue(&vq->poll);
 			} else if (unlikely(vhost_enable_notify(&net->dev, vq))) {
@@ -528,6 +527,9 @@ static void handle_tx(struct vhost_net *net)
 			}
 			break;
 		}
+		/* On error, stop handling until the next kick. */
+		if (unlikely(err < 0))
+			break;
 		if (in) {
 			vq_err(vq, "Unexpected descriptor format for TX: "
 			       "out %d, int %d\n", out, in);
@@ -555,7 +557,8 @@ static void handle_tx(struct vhost_net *net)
 			struct ubuf_info *ubuf;
 			ubuf = nvq->ubuf_info + nvq->upend_idx;
 
-			vq->heads[nvq->upend_idx].id = cpu_to_vhost32(vq, head);
+			vq->heads[nvq->upend_idx].id =
+				cpu_to_vhost32(vq, used.id);
 			vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
 			ubuf->callback = vhost_zerocopy_callback;
 			ubuf->ctx = nvq->ubufs;
@@ -596,7 +599,7 @@ static void handle_tx(struct vhost_net *net)
 			pr_debug("Truncated TX packet: "
 				 " len %d != %zd\n", err, len);
 		if (!zcopy_used)
-			vhost_add_used_and_signal(&net->dev, vq, head, 0);
+			vhost_add_used_and_signal(&net->dev, vq, &used, 0);
 		else
 			vhost_zerocopy_signal_used(net, vq);
 		vhost_net_tx_packet(net);
@@ -754,17 +757,15 @@ static void handle_rx(struct vhost_net *net)
 						      &busyloop_intr))) {
 		sock_len += sock_hlen;
 		vhost_len = sock_len + vhost_hlen;
-		headcount = vhost_get_bufs(vq, vq->heads + nvq->done_idx,
-					   vhost_len, &in, vq_log, &log,
-					   likely(mergeable) ? UIO_MAXIOV : 1);
-		/* On error, stop handling until the next kick. */
-		if (unlikely(headcount < 0))
-			goto out;
+		err = vhost_get_bufs(vq, vq->heads + nvq->done_idx,
+				     vhost_len, &in, vq_log, &log,
+				     likely(mergeable) ? UIO_MAXIOV : 1,
+				     &headcount);
 		/* OK, now we need to know about added descriptors. */
-		if (!headcount) {
+		if (err == -ENOSPC) {
 			if (unlikely(busyloop_intr)) {
 				vhost_poll_queue(&vq->poll);
-			} else if (unlikely(vhost_enable_notify(&net->dev, vq))) {
+			}else if (unlikely(vhost_enable_notify(&net->dev, vq))) {
 				/* They have slipped one in as we were
 				 * doing that: check again. */
 				vhost_disable_notify(&net->dev, vq);
@@ -775,6 +776,9 @@ static void handle_rx(struct vhost_net *net)
 			goto out;
 		}
 		busyloop_intr = false;
+		/* On error, stop handling until the next kick. */
+		if (unlikely(err < 0))
+			goto out;
 		if (nvq->rx_ring)
 			msg.msg_control = vhost_net_buf_consume(&nvq->rxq);
 		/* On overrun, truncate and discard */
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 17fcd3b..013464c 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -67,7 +67,7 @@ struct vhost_scsi_inflight {
 
 struct vhost_scsi_cmd {
 	/* Descriptor from vhost_get_vq_desc() for virt_queue segment */
-	int tvc_vq_desc;
+	struct vring_used_elem tvc_vq_used;
 	/* virtio-scsi initiator task attribute */
 	int tvc_task_attr;
 	/* virtio-scsi response incoming iovecs */
@@ -441,8 +441,9 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
 	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
 	struct virtio_scsi_event *event = &evt->event;
 	struct virtio_scsi_event __user *eventp;
+	struct vring_used_elem used;
 	unsigned out, in;
-	int head, ret;
+	int ret;
 
 	if (!vq->private_data) {
 		vs->vs_events_missed = true;
@@ -451,16 +452,16 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
 
 again:
 	vhost_disable_notify(&vs->dev, vq);
-	head = vhost_get_vq_desc(vq, vq->iov,
+	ret = vhost_get_vq_desc(vq, &used, vq->iov,
 			ARRAY_SIZE(vq->iov), &out, &in,
 			NULL, NULL);
-	if (head < 0) {
+	if (ret == -ENOSPC) {
+		if (vhost_enable_notify(&vs->dev, vq))
+			goto again;
 		vs->vs_events_missed = true;
 		return;
 	}
-	if (head == vq->num) {
-		if (vhost_enable_notify(&vs->dev, vq))
-			goto again;
+	if (ret < 0) {
 		vs->vs_events_missed = true;
 		return;
 	}
@@ -480,7 +481,7 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
 	eventp = vq->iov[out].iov_base;
 	ret = __copy_to_user(eventp, event, sizeof(*event));
 	if (!ret)
-		vhost_add_used_and_signal(&vs->dev, vq, head, 0);
+		vhost_add_used_and_signal(&vs->dev, vq, &used, 0);
 	else
 		vq_err(vq, "Faulted on vhost_scsi_send_event\n");
 }
@@ -541,7 +542,7 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
 		ret = copy_to_iter(&v_rsp, sizeof(v_rsp), &iov_iter);
 		if (likely(ret == sizeof(v_rsp))) {
 			struct vhost_scsi_virtqueue *q;
-			vhost_add_used(cmd->tvc_vq, cmd->tvc_vq_desc, 0);
+			vhost_add_used(cmd->tvc_vq, &cmd->tvc_vq_used, 0);
 			q = container_of(cmd->tvc_vq, struct vhost_scsi_virtqueue, vq);
 			vq = q - vs->vqs;
 			__set_bit(vq, signal);
@@ -784,7 +785,7 @@ static void vhost_scsi_submission_work(struct work_struct *work)
 static void
 vhost_scsi_send_bad_target(struct vhost_scsi *vs,
 			   struct vhost_virtqueue *vq,
-			   int head, unsigned out)
+			   struct vring_used_elem *used, unsigned out)
 {
 	struct virtio_scsi_cmd_resp __user *resp;
 	struct virtio_scsi_cmd_resp rsp;
@@ -795,7 +796,7 @@ vhost_scsi_send_bad_target(struct vhost_scsi *vs,
 	resp = vq->iov[out].iov_base;
 	ret = __copy_to_user(resp, &rsp, sizeof(rsp));
 	if (!ret)
-		vhost_add_used_and_signal(&vs->dev, vq, head, 0);
+		vhost_add_used_and_signal(&vs->dev, vq, used, 0);
 	else
 		pr_err("Faulted on virtio_scsi_cmd_resp\n");
 }
@@ -807,11 +808,12 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 	struct virtio_scsi_cmd_req v_req;
 	struct virtio_scsi_cmd_req_pi v_req_pi;
 	struct vhost_scsi_cmd *cmd;
+	struct vring_used_elem used;
 	struct iov_iter out_iter, in_iter, prot_iter, data_iter;
 	u64 tag;
 	u32 exp_data_len, data_direction;
 	unsigned int out = 0, in = 0;
-	int head, ret, prot_bytes;
+	int ret, prot_bytes;
 	size_t req_size, rsp_size = sizeof(struct virtio_scsi_cmd_resp);
 	size_t out_size, in_size;
 	u16 lun;
@@ -831,22 +833,22 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 	vhost_disable_notify(&vs->dev, vq);
 
 	for (;;) {
-		head = vhost_get_vq_desc(vq, vq->iov,
-					 ARRAY_SIZE(vq->iov), &out, &in,
-					 NULL, NULL);
+		ret = vhost_get_vq_desc(vq, &used, vq->iov,
+					ARRAY_SIZE(vq->iov), &out, &in,
+					NULL, NULL);
 		pr_debug("vhost_get_vq_desc: head: %d, out: %u in: %u\n",
-			 head, out, in);
-		/* On error, stop handling until the next kick. */
-		if (unlikely(head < 0))
-			break;
+			 used.id, out, in);
 		/* Nothing new?  Wait for eventfd to tell us they refilled. */
-		if (head == vq->num) {
+		if (ret == -ENOSPC) {
 			if (unlikely(vhost_enable_notify(&vs->dev, vq))) {
 				vhost_disable_notify(&vs->dev, vq);
 				continue;
 			}
 			break;
 		}
+		/* On error, stop handling until the next kick. */
+		if (unlikely(ret < 0))
+			break;
 		/*
 		 * Check for a sane response buffer so we can report early
 		 * errors back to the guest.
@@ -891,20 +893,20 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 
 		if (unlikely(!copy_from_iter_full(req, req_size, &out_iter))) {
 			vq_err(vq, "Faulted on copy_from_iter\n");
-			vhost_scsi_send_bad_target(vs, vq, head, out);
+			vhost_scsi_send_bad_target(vs, vq, &used, out);
 			continue;
 		}
 		/* virtio-scsi spec requires byte 0 of the lun to be 1 */
 		if (unlikely(*lunp != 1)) {
 			vq_err(vq, "Illegal virtio-scsi lun: %u\n", *lunp);
-			vhost_scsi_send_bad_target(vs, vq, head, out);
+			vhost_scsi_send_bad_target(vs, vq, &used, out);
 			continue;
 		}
 
 		tpg = READ_ONCE(vs_tpg[*target]);
 		if (unlikely(!tpg)) {
 			/* Target does not exist, fail the request */
-			vhost_scsi_send_bad_target(vs, vq, head, out);
+			vhost_scsi_send_bad_target(vs, vq, &used, out);
 			continue;
 		}
 		/*
@@ -950,7 +952,8 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 				if (data_direction != DMA_TO_DEVICE) {
 					vq_err(vq, "Received non zero pi_bytesout,"
 						" but wrong data_direction\n");
-					vhost_scsi_send_bad_target(vs, vq, head, out);
+					vhost_scsi_send_bad_target(vs, vq,
+								   &used, out);
 					continue;
 				}
 				prot_bytes = vhost32_to_cpu(vq, v_req_pi.pi_bytesout);
@@ -958,7 +961,8 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 				if (data_direction != DMA_FROM_DEVICE) {
 					vq_err(vq, "Received non zero pi_bytesin,"
 						" but wrong data_direction\n");
-					vhost_scsi_send_bad_target(vs, vq, head, out);
+					vhost_scsi_send_bad_target(vs, vq,
+								   &used, out);
 					continue;
 				}
 				prot_bytes = vhost32_to_cpu(vq, v_req_pi.pi_bytesin);
@@ -996,7 +1000,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 			vq_err(vq, "Received SCSI CDB with command_size: %d that"
 				" exceeds SCSI_MAX_VARLEN_CDB_SIZE: %d\n",
 				scsi_command_size(cdb), VHOST_SCSI_MAX_CDB_SIZE);
-			vhost_scsi_send_bad_target(vs, vq, head, out);
+			vhost_scsi_send_bad_target(vs, vq, &used, out);
 			continue;
 		}
 		cmd = vhost_scsi_get_tag(vq, tpg, cdb, tag, lun, task_attr,
@@ -1005,7 +1009,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 		if (IS_ERR(cmd)) {
 			vq_err(vq, "vhost_scsi_get_tag failed %ld\n",
 			       PTR_ERR(cmd));
-			vhost_scsi_send_bad_target(vs, vq, head, out);
+			vhost_scsi_send_bad_target(vs, vq, &used, out);
 			continue;
 		}
 		cmd->tvc_vhost = vs;
@@ -1025,7 +1029,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 			if (unlikely(ret)) {
 				vq_err(vq, "Failed to map iov to sgl\n");
 				vhost_scsi_release_cmd(&cmd->tvc_se_cmd);
-				vhost_scsi_send_bad_target(vs, vq, head, out);
+				vhost_scsi_send_bad_target(vs, vq, &used, out);
 				continue;
 			}
 		}
@@ -1034,7 +1038,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 		 * complete the virtio-scsi request in TCM callback context via
 		 * vhost_scsi_queue_data_in() and vhost_scsi_queue_status()
 		 */
-		cmd->tvc_vq_desc = head;
+		cmd->tvc_vq_used = used;
 		/*
 		 * Dispatch cmd descriptor for cmwq execution in process
 		 * context provided by vhost_scsi_workqueue.  This also ensures
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 8814e5b..9572c4f 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1962,6 +1962,7 @@ static int get_indirect(struct vhost_virtqueue *vq,
  * never a valid descriptor number) if none was found.  A negative code is
  * returned on error. */
 int vhost_get_vq_desc(struct vhost_virtqueue *vq,
+		      struct vring_used_elem *used,
 		      struct iovec iov[], unsigned int iov_size,
 		      unsigned int *out_num, unsigned int *in_num,
 		      struct vhost_log *log, unsigned int *log_num)
@@ -1994,7 +1995,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 		 * invalid.
 		 */
 		if (vq->avail_idx == last_avail_idx)
-			return vq->num;
+			return -ENOSPC;
 
 		/* Only get avail ring entries after they have been
 		 * exposed by guest.
@@ -2012,6 +2013,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 		return -EFAULT;
 	}
 
+	used->id = ring_head;
 	head = vhost16_to_cpu(vq, ring_head);
 
 	/* If their number is silly, that's an error. */
@@ -2100,10 +2102,16 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 	/* Assume notifications from guest are disabled at this point,
 	 * if they aren't we would need to update avail_event index. */
 	BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
-	return head;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
 
+static void vhost_set_used_len(struct vhost_virtqueue *vq,
+			       struct vring_used_elem *used, int len)
+{
+	used->len = cpu_to_vhost32(vq, len);
+}
+
 /* This is a multi-buffer version of vhost_get_desc, that works if
  *	vq has read descriptors only.
  * @vq		- the relevant virtqueue
@@ -2120,13 +2128,13 @@ int vhost_get_bufs(struct vhost_virtqueue *vq,
 		   unsigned *iovcount,
 		   struct vhost_log *log,
 		   unsigned *log_num,
-		   unsigned int quota)
+		   unsigned int quota,
+		   s16 *count)
 {
 	unsigned int out, in;
 	int seg = 0;
 	int headcount = 0;
-	unsigned d;
-	int r, nlogs = 0;
+	int r = 0, nlogs = 0;
 	/* len is always initialized before use since we are always called with
 	 * datalen > 0.
 	 */
@@ -2137,17 +2145,12 @@ int vhost_get_bufs(struct vhost_virtqueue *vq,
 			r = -ENOBUFS;
 			goto err;
 		}
-		r = vhost_get_vq_desc(vq, vq->iov + seg,
+		r = vhost_get_vq_desc(vq, &heads[headcount], vq->iov + seg,
 				      ARRAY_SIZE(vq->iov) - seg, &out,
 				      &in, log, log_num);
 		if (unlikely(r < 0))
 			goto err;
 
-		d = r;
-		if (d == vq->num) {
-			r = 0;
-			goto err;
-		}
 		if (unlikely(out || in <= 0)) {
 			vq_err(vq, "unexpected descriptor format for RX: "
 				"out %d, in %d\n", out, in);
@@ -2158,24 +2161,26 @@ int vhost_get_bufs(struct vhost_virtqueue *vq,
 			nlogs += *log_num;
 			log += *log_num;
 		}
-		heads[headcount].id = cpu_to_vhost32(vq, d);
+
 		len = iov_length(vq->iov + seg, in);
-		heads[headcount].len = cpu_to_vhost32(vq, len);
+		vhost_set_used_len(vq, &heads[headcount], len);
 		datalen -= len;
 		++headcount;
 		seg += in;
 	}
-	heads[headcount - 1].len = cpu_to_vhost32(vq, len + datalen);
+	vhost_set_used_len(vq, &heads[headcount - 1], len + datalen);
 	*iovcount = seg;
 	if (unlikely(log))
 		*log_num = nlogs;
 
 	/* Detect overrun */
 	if (unlikely(datalen > 0)) {
-		r = UIO_MAXIOV + 1;
+		headcount = UIO_MAXIOV + 1;
 		goto err;
 	}
-	return headcount;
+
+	*count = headcount;
+	return 0;
 err:
 	vhost_discard_vq_desc(vq, headcount);
 	return r;
@@ -2191,14 +2196,11 @@ EXPORT_SYMBOL_GPL(vhost_discard_vq_desc);
 
 /* After we've used one of their buffers, we tell them about it.  We'll then
  * want to notify the guest, using eventfd. */
-int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
+int vhost_add_used(struct vhost_virtqueue *vq, struct vring_used_elem *used,
+		   int len)
 {
-	struct vring_used_elem heads = {
-		cpu_to_vhost32(vq, head),
-		cpu_to_vhost32(vq, len)
-	};
-
-	return vhost_add_used_n(vq, &heads, 1);
+	vhost_set_used_len(vq, used, len);
+	return vhost_add_used_n(vq, used, 1);
 }
 EXPORT_SYMBOL_GPL(vhost_add_used);
 
@@ -2331,9 +2333,9 @@ EXPORT_SYMBOL_GPL(vhost_signal);
 /* And here's the combo meal deal.  Supersize me! */
 void vhost_add_used_and_signal(struct vhost_dev *dev,
 			       struct vhost_virtqueue *vq,
-			       unsigned int head, int len)
+			       struct vring_used_elem *used, int len)
 {
-	vhost_add_used(vq, head, len);
+	vhost_add_used(vq, used, len);
 	vhost_signal(dev, vq);
 }
 EXPORT_SYMBOL_GPL(vhost_add_used_and_signal);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 52edd242..a7cc7e7 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -182,6 +182,7 @@ bool vhost_vq_access_ok(struct vhost_virtqueue *vq);
 bool vhost_log_access_ok(struct vhost_dev *);
 
 int vhost_get_vq_desc(struct vhost_virtqueue *,
+		      struct vring_used_elem *used_elem,
 		      struct iovec iov[], unsigned int iov_count,
 		      unsigned int *out_num, unsigned int *in_num,
 		      struct vhost_log *log, unsigned int *log_num);
@@ -191,15 +192,17 @@ int vhost_get_bufs(struct vhost_virtqueue *vq,
 		   unsigned *iovcount,
 		   struct vhost_log *log,
 		   unsigned *log_num,
-		   unsigned int quota);
+		   unsigned int quota,
+		   s16 *count);
 void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
 
 int vhost_vq_init_access(struct vhost_virtqueue *);
-int vhost_add_used(struct vhost_virtqueue *, unsigned int head, int len);
+int vhost_add_used(struct vhost_virtqueue *vq,
+		   struct vring_used_elem *elem, int len);
 int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads,
 		     unsigned count);
 void vhost_add_used_and_signal(struct vhost_dev *, struct vhost_virtqueue *,
-			       unsigned int id, int len);
+			       struct vring_used_elem *, int len);
 void vhost_add_used_and_signal_n(struct vhost_dev *, struct vhost_virtqueue *,
 			       struct vring_used_elem *heads, unsigned count);
 void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 34bc3ab..59a01cd 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -98,11 +98,12 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 
 	for (;;) {
 		struct virtio_vsock_pkt *pkt;
+		struct vring_used_elem used;
 		struct iov_iter iov_iter;
 		unsigned out, in;
 		size_t nbytes;
 		size_t len;
-		int head;
+		int ret;
 
 		spin_lock_bh(&vsock->send_pkt_list_lock);
 		if (list_empty(&vsock->send_pkt_list)) {
@@ -116,16 +117,9 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 		list_del_init(&pkt->list);
 		spin_unlock_bh(&vsock->send_pkt_list_lock);
 
-		head = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
-					 &out, &in, NULL, NULL);
-		if (head < 0) {
-			spin_lock_bh(&vsock->send_pkt_list_lock);
-			list_add(&pkt->list, &vsock->send_pkt_list);
-			spin_unlock_bh(&vsock->send_pkt_list_lock);
-			break;
-		}
-
-		if (head == vq->num) {
+		ret = vhost_get_vq_desc(vq, &used, vq->iov, ARRAY_SIZE(vq->iov),
+					&out, &in, NULL, NULL);
+		if (ret == -ENOSPC) {
 			spin_lock_bh(&vsock->send_pkt_list_lock);
 			list_add(&pkt->list, &vsock->send_pkt_list);
 			spin_unlock_bh(&vsock->send_pkt_list_lock);
@@ -139,6 +133,12 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 			}
 			break;
 		}
+		if (ret < 0) {
+			spin_lock_bh(&vsock->send_pkt_list_lock);
+			list_add(&pkt->list, &vsock->send_pkt_list);
+			spin_unlock_bh(&vsock->send_pkt_list_lock);
+			break;
+		}
 
 		if (out) {
 			virtio_transport_free_pkt(pkt);
@@ -146,7 +146,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 			break;
 		}
 
-		len = iov_length(&vq->iov[out], in);
+		len = vhost32_to_cpu(vq, used.len);
 		iov_iter_init(&iov_iter, READ, &vq->iov[out], in, len);
 
 		nbytes = copy_to_iter(&pkt->hdr, sizeof(pkt->hdr), &iov_iter);
@@ -163,7 +163,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 			break;
 		}
 
-		vhost_add_used(vq, head, sizeof(pkt->hdr) + pkt->len);
+		vhost_add_used(vq, &used, sizeof(pkt->hdr) + pkt->len);
 		added = true;
 
 		if (pkt->reply) {
@@ -346,7 +346,8 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 	struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
 						 dev);
 	struct virtio_vsock_pkt *pkt;
-	int head;
+	struct vring_used_elem used;
+	int ret;
 	unsigned int out, in;
 	bool added = false;
 
@@ -367,18 +368,17 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 			goto no_more_replies;
 		}
 
-		head = vhost_get_vq_desc(vq, vq->iov, ARRAY_SIZE(vq->iov),
-					 &out, &in, NULL, NULL);
-		if (head < 0)
-			break;
-
-		if (head == vq->num) {
+		ret = vhost_get_vq_desc(vq, &used, vq->iov, ARRAY_SIZE(vq->iov),
+					&out, &in, NULL, NULL);
+		if (ret == -ENOSPC) {
 			if (unlikely(vhost_enable_notify(&vsock->dev, vq))) {
 				vhost_disable_notify(&vsock->dev, vq);
 				continue;
 			}
 			break;
 		}
+		if (ret < 0)
+			break;
 
 		pkt = vhost_vsock_alloc_pkt(vq, out, in);
 		if (!pkt) {
@@ -397,7 +397,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 		else
 			virtio_transport_free_pkt(pkt);
 
-		vhost_add_used(vq, head, sizeof(pkt->hdr) + len);
+		vhost_add_used(vq, &used, sizeof(pkt->hdr) + len);
 		added = true;
 	}
 
-- 
2.7.4

[PATCH net-next V2 3/8] vhost: do not use vring_used_elem

From: Jason Wang <hidden>
Date: 2018-07-16 03:28:43 

Instead of depending on the exported vring_used_elem, this patch
switches to use a new internal structure vhost_used_elem which embed
vring_used_elem in itself. This could be used to let vhost to record
extra metadata for the incoming packed ring layout.

Signed-off-by: Jason Wang <redacted>
---
 drivers/vhost/net.c   | 19 +++++++-------
 drivers/vhost/scsi.c  | 10 ++++----
 drivers/vhost/vhost.c | 68 ++++++++++++---------------------------------------
 drivers/vhost/vhost.h | 18 ++++++++------
 drivers/vhost/vsock.c |  6 ++---
 5 files changed, 45 insertions(+), 76 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index a8c9506..2f1395a 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -348,10 +348,10 @@ static void vhost_zerocopy_signal_used(struct vhost_net *net,
 	int j = 0;
 
 	for (i = nvq->done_idx; i != nvq->upend_idx; i = (i + 1) % UIO_MAXIOV) {
-		if (vq->heads[i].len == VHOST_DMA_FAILED_LEN)
+		if (vq->heads[i].elem.len == VHOST_DMA_FAILED_LEN)
 			vhost_net_tx_err(net);
-		if (VHOST_DMA_IS_DONE(vq->heads[i].len)) {
-			vq->heads[i].len = VHOST_DMA_CLEAR_LEN;
+		if (VHOST_DMA_IS_DONE(vq->heads[i].elem.len)) {
+			vq->heads[i].elem.len = VHOST_DMA_CLEAR_LEN;
 			++j;
 		} else
 			break;
@@ -374,7 +374,7 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success)
 	rcu_read_lock_bh();
 
 	/* set len to mark this desc buffers done DMA */
-	vq->heads[ubuf->desc].len = success ?
+	vq->heads[ubuf->desc].elem.len = success ?
 		VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN;
 	cnt = vhost_net_ubuf_put(ubufs);
 
@@ -430,7 +430,7 @@ static int vhost_net_enable_vq(struct vhost_net *n,
 
 static int vhost_net_tx_get_vq_desc(struct vhost_net *net,
 				    struct vhost_virtqueue *vq,
-				    struct vring_used_elem *used_elem,
+				    struct vhost_used_elem *used_elem,
 				    struct iovec iov[], unsigned int iov_size,
 				    unsigned int *out_num, unsigned int *in_num,
 				    bool *busyloop_intr)
@@ -488,7 +488,7 @@ static void handle_tx(struct vhost_net *net)
 	size_t hdr_size;
 	struct socket *sock;
 	struct vhost_net_ubuf_ref *uninitialized_var(ubufs);
-	struct vring_used_elem used;
+	struct vhost_used_elem used;
 	bool zcopy, zcopy_used;
 	int sent_pkts = 0;
 
@@ -557,9 +557,10 @@ static void handle_tx(struct vhost_net *net)
 			struct ubuf_info *ubuf;
 			ubuf = nvq->ubuf_info + nvq->upend_idx;
 
-			vq->heads[nvq->upend_idx].id =
-				cpu_to_vhost32(vq, used.id);
-			vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
+			vq->heads[nvq->upend_idx].elem.id =
+				cpu_to_vhost32(vq, used.elem.id);
+			vq->heads[nvq->upend_idx].elem.len =
+				VHOST_DMA_IN_PROGRESS;
 			ubuf->callback = vhost_zerocopy_callback;
 			ubuf->ctx = nvq->ubufs;
 			ubuf->desc = nvq->upend_idx;
diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 013464c..149c38c 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -67,7 +67,7 @@ struct vhost_scsi_inflight {
 
 struct vhost_scsi_cmd {
 	/* Descriptor from vhost_get_vq_desc() for virt_queue segment */
-	struct vring_used_elem tvc_vq_used;
+	struct vhost_used_elem tvc_vq_used;
 	/* virtio-scsi initiator task attribute */
 	int tvc_task_attr;
 	/* virtio-scsi response incoming iovecs */
@@ -441,7 +441,7 @@ vhost_scsi_do_evt_work(struct vhost_scsi *vs, struct vhost_scsi_evt *evt)
 	struct vhost_virtqueue *vq = &vs->vqs[VHOST_SCSI_VQ_EVT].vq;
 	struct virtio_scsi_event *event = &evt->event;
 	struct virtio_scsi_event __user *eventp;
-	struct vring_used_elem used;
+	struct vhost_used_elem used;
 	unsigned out, in;
 	int ret;
 
@@ -785,7 +785,7 @@ static void vhost_scsi_submission_work(struct work_struct *work)
 static void
 vhost_scsi_send_bad_target(struct vhost_scsi *vs,
 			   struct vhost_virtqueue *vq,
-			   struct vring_used_elem *used, unsigned out)
+			   struct vhost_used_elem *used, unsigned out)
 {
 	struct virtio_scsi_cmd_resp __user *resp;
 	struct virtio_scsi_cmd_resp rsp;
@@ -808,7 +808,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 	struct virtio_scsi_cmd_req v_req;
 	struct virtio_scsi_cmd_req_pi v_req_pi;
 	struct vhost_scsi_cmd *cmd;
-	struct vring_used_elem used;
+	struct vhost_used_elem used;
 	struct iov_iter out_iter, in_iter, prot_iter, data_iter;
 	u64 tag;
 	u32 exp_data_len, data_direction;
@@ -837,7 +837,7 @@ vhost_scsi_handle_vq(struct vhost_scsi *vs, struct vhost_virtqueue *vq)
 					ARRAY_SIZE(vq->iov), &out, &in,
 					NULL, NULL);
 		pr_debug("vhost_get_vq_desc: head: %d, out: %u in: %u\n",
-			 used.id, out, in);
+			 used.elem.id, out, in);
 		/* Nothing new?  Wait for eventfd to tell us they refilled. */
 		if (ret == -ENOSPC) {
 			if (unlikely(vhost_enable_notify(&vs->dev, vq))) {
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 9572c4f..641f4c6 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -731,41 +731,6 @@ static bool memory_access_ok(struct vhost_dev *d, struct vhost_umem *umem,
 static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
 			  struct iovec iov[], int iov_size, int access);
 
-static int vhost_copy_to_user(struct vhost_virtqueue *vq, void __user *to,
-			      const void *from, unsigned size)
-{
-	int ret;
-
-	if (!vq->iotlb)
-		return __copy_to_user(to, from, size);
-	else {
-		/* This function should be called after iotlb
-		 * prefetch, which means we're sure that all vq
-		 * could be access through iotlb. So -EAGAIN should
-		 * not happen in this case.
-		 */
-		struct iov_iter t;
-		void __user *uaddr = vhost_vq_meta_fetch(vq,
-				     (u64)(uintptr_t)to, size,
-				     VHOST_ADDR_USED);
-
-		if (uaddr)
-			return __copy_to_user(uaddr, from, size);
-
-		ret = translate_desc(vq, (u64)(uintptr_t)to, size, vq->iotlb_iov,
-				     ARRAY_SIZE(vq->iotlb_iov),
-				     VHOST_ACCESS_WO);
-		if (ret < 0)
-			goto out;
-		iov_iter_init(&t, WRITE, vq->iotlb_iov, ret, size);
-		ret = copy_to_iter(from, size, &t);
-		if (ret == size)
-			ret = 0;
-	}
-out:
-	return ret;
-}
-
 static int vhost_copy_from_user(struct vhost_virtqueue *vq, void *to,
 				void __user *from, unsigned size)
 {
@@ -1962,7 +1927,7 @@ static int get_indirect(struct vhost_virtqueue *vq,
  * never a valid descriptor number) if none was found.  A negative code is
  * returned on error. */
 int vhost_get_vq_desc(struct vhost_virtqueue *vq,
-		      struct vring_used_elem *used,
+		      struct vhost_used_elem *used,
 		      struct iovec iov[], unsigned int iov_size,
 		      unsigned int *out_num, unsigned int *in_num,
 		      struct vhost_log *log, unsigned int *log_num)
@@ -2013,7 +1978,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 		return -EFAULT;
 	}
 
-	used->id = ring_head;
+	used->elem.id = ring_head;
 	head = vhost16_to_cpu(vq, ring_head);
 
 	/* If their number is silly, that's an error. */
@@ -2107,9 +2072,9 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
 
 static void vhost_set_used_len(struct vhost_virtqueue *vq,
-			       struct vring_used_elem *used, int len)
+			       struct vhost_used_elem *used, int len)
 {
-	used->len = cpu_to_vhost32(vq, len);
+	used->elem.len = cpu_to_vhost32(vq, len);
 }
 
 /* This is a multi-buffer version of vhost_get_desc, that works if
@@ -2123,7 +2088,7 @@ static void vhost_set_used_len(struct vhost_virtqueue *vq,
  *	returns number of buffer heads allocated, negative on error
  */
 int vhost_get_bufs(struct vhost_virtqueue *vq,
-		   struct vring_used_elem *heads,
+		   struct vhost_used_elem *heads,
 		   int datalen,
 		   unsigned *iovcount,
 		   struct vhost_log *log,
@@ -2196,7 +2161,7 @@ EXPORT_SYMBOL_GPL(vhost_discard_vq_desc);
 
 /* After we've used one of their buffers, we tell them about it.  We'll then
  * want to notify the guest, using eventfd. */
-int vhost_add_used(struct vhost_virtqueue *vq, struct vring_used_elem *used,
+int vhost_add_used(struct vhost_virtqueue *vq, struct vhost_used_elem *used,
 		   int len)
 {
 	vhost_set_used_len(vq, used, len);
@@ -2205,27 +2170,26 @@ int vhost_add_used(struct vhost_virtqueue *vq, struct vring_used_elem *used,
 EXPORT_SYMBOL_GPL(vhost_add_used);
 
 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
-			    struct vring_used_elem *heads,
+			    struct vhost_used_elem *heads,
 			    unsigned count)
 {
 	struct vring_used_elem __user *used;
 	u16 old, new;
-	int start;
+	int start, i;
 
 	start = vq->last_used_idx & (vq->num - 1);
 	used = vq->used->ring + start;
-	if (count == 1) {
-		if (vhost_put_user(vq, heads[0].id, &used->id)) {
+	for (i = 0; i < count; i++) {
+		if (unlikely(vhost_put_user(vq, heads[i].elem.id,
+					    &used[i].id))) {
 			vq_err(vq, "Failed to write used id");
 			return -EFAULT;
 		}
-		if (vhost_put_user(vq, heads[0].len, &used->len)) {
+		if (unlikely(vhost_put_user(vq, heads[i].elem.len,
+					    &used[i].len))) {
 			vq_err(vq, "Failed to write used len");
 			return -EFAULT;
 		}
-	} else if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) {
-		vq_err(vq, "Failed to write used");
-		return -EFAULT;
 	}
 	if (unlikely(vq->log_used)) {
 		/* Make sure data is seen before log. */
@@ -2249,7 +2213,7 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,
 
 /* After we've used one of their buffers, we tell them about it.  We'll then
  * want to notify the guest, using eventfd. */
-int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
+int vhost_add_used_n(struct vhost_virtqueue *vq, struct vhost_used_elem *heads,
 		     unsigned count)
 {
 	int start, n, r;
@@ -2333,7 +2297,7 @@ EXPORT_SYMBOL_GPL(vhost_signal);
 /* And here's the combo meal deal.  Supersize me! */
 void vhost_add_used_and_signal(struct vhost_dev *dev,
 			       struct vhost_virtqueue *vq,
-			       struct vring_used_elem *used, int len)
+			       struct vhost_used_elem *used, int len)
 {
 	vhost_add_used(vq, used, len);
 	vhost_signal(dev, vq);
@@ -2343,7 +2307,7 @@ EXPORT_SYMBOL_GPL(vhost_add_used_and_signal);
 /* multi-buffer version of vhost_add_used_and_signal */
 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
 				 struct vhost_virtqueue *vq,
-				 struct vring_used_elem *heads, unsigned count)
+				 struct vhost_used_elem *heads, unsigned count)
 {
 	vhost_add_used_n(vq, heads, count);
 	vhost_signal(dev, vq);
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index a7cc7e7..8dea44b 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -34,6 +34,10 @@ struct vhost_poll {
 	struct vhost_dev	 *dev;
 };
 
+struct vhost_used_elem {
+	struct vring_used_elem elem;
+};
+
 void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn);
 void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work);
 bool vhost_has_work(struct vhost_dev *dev);
@@ -126,7 +130,7 @@ struct vhost_virtqueue {
 	struct iovec iov[UIO_MAXIOV];
 	struct iovec iotlb_iov[64];
 	struct iovec *indirect;
-	struct vring_used_elem *heads;
+	struct vhost_used_elem *heads;
 	/* Protected by virtqueue mutex. */
 	struct vhost_umem *umem;
 	struct vhost_umem *iotlb;
@@ -182,12 +186,12 @@ bool vhost_vq_access_ok(struct vhost_virtqueue *vq);
 bool vhost_log_access_ok(struct vhost_dev *);
 
 int vhost_get_vq_desc(struct vhost_virtqueue *,
-		      struct vring_used_elem *used_elem,
+		      struct vhost_used_elem *used_elem,
 		      struct iovec iov[], unsigned int iov_count,
 		      unsigned int *out_num, unsigned int *in_num,
 		      struct vhost_log *log, unsigned int *log_num);
 int vhost_get_bufs(struct vhost_virtqueue *vq,
-		   struct vring_used_elem *heads,
+		   struct vhost_used_elem *heads,
 		   int datalen,
 		   unsigned *iovcount,
 		   struct vhost_log *log,
@@ -198,13 +202,13 @@ void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
 
 int vhost_vq_init_access(struct vhost_virtqueue *);
 int vhost_add_used(struct vhost_virtqueue *vq,
-		   struct vring_used_elem *elem, int len);
-int vhost_add_used_n(struct vhost_virtqueue *, struct vring_used_elem *heads,
+		   struct vhost_used_elem *elem, int len);
+int vhost_add_used_n(struct vhost_virtqueue *vq, struct vhost_used_elem *heads,
 		     unsigned count);
 void vhost_add_used_and_signal(struct vhost_dev *, struct vhost_virtqueue *,
-			       struct vring_used_elem *, int len);
+			       struct vhost_used_elem *, int len);
 void vhost_add_used_and_signal_n(struct vhost_dev *, struct vhost_virtqueue *,
-			       struct vring_used_elem *heads, unsigned count);
+			       struct vhost_used_elem *heads, unsigned count);
 void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
 void vhost_disable_notify(struct vhost_dev *, struct vhost_virtqueue *);
 bool vhost_vq_avail_empty(struct vhost_dev *, struct vhost_virtqueue *);
diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 59a01cd..695694f 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -98,7 +98,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 
 	for (;;) {
 		struct virtio_vsock_pkt *pkt;
-		struct vring_used_elem used;
+		struct vhost_used_elem used;
 		struct iov_iter iov_iter;
 		unsigned out, in;
 		size_t nbytes;
@@ -146,7 +146,7 @@ vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
 			break;
 		}
 
-		len = vhost32_to_cpu(vq, used.len);
+		len = vhost32_to_cpu(vq, used.elem.len);
 		iov_iter_init(&iov_iter, READ, &vq->iov[out], in, len);
 
 		nbytes = copy_to_iter(&pkt->hdr, sizeof(pkt->hdr), &iov_iter);
@@ -346,7 +346,7 @@ static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
 	struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
 						 dev);
 	struct virtio_vsock_pkt *pkt;
-	struct vring_used_elem used;
+	struct vhost_used_elem used;
 	int ret;
 	unsigned int out, in;
 	bool added = false;
-- 
2.7.4

[PATCH net-next V2 4/8] vhost_net: do not explicitly manipulate vhost_used_elem

From: Jason Wang <hidden>
Date: 2018-07-16 03:28:47 

Two helpers of setting/getting used len were introduced to avoid
explicitly manipulating vhost_used_elem in zerocopy code. This will be
used to hide used_elem internals and simplify packed ring
implementation.

Signed-off-by: Jason Wang <redacted>
---
 drivers/vhost/net.c   | 11 +++++------
 drivers/vhost/vhost.c | 12 ++++++++++--
 drivers/vhost/vhost.h |  5 +++++
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 2f1395a..2432002 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -348,9 +348,10 @@ static void vhost_zerocopy_signal_used(struct vhost_net *net,
 	int j = 0;
 
 	for (i = nvq->done_idx; i != nvq->upend_idx; i = (i + 1) % UIO_MAXIOV) {
-		if (vq->heads[i].elem.len == VHOST_DMA_FAILED_LEN)
+		if (vhost_get_used_len(vq, &vq->heads[i]) ==
+		    VHOST_DMA_FAILED_LEN)
 			vhost_net_tx_err(net);
-		if (VHOST_DMA_IS_DONE(vq->heads[i].elem.len)) {
+		if (VHOST_DMA_IS_DONE(vhost_get_used_len(vq, &vq->heads[i]))) {
 			vq->heads[i].elem.len = VHOST_DMA_CLEAR_LEN;
 			++j;
 		} else
@@ -557,10 +558,8 @@ static void handle_tx(struct vhost_net *net)
 			struct ubuf_info *ubuf;
 			ubuf = nvq->ubuf_info + nvq->upend_idx;
 
-			vq->heads[nvq->upend_idx].elem.id =
-				cpu_to_vhost32(vq, used.elem.id);
-			vq->heads[nvq->upend_idx].elem.len =
-				VHOST_DMA_IN_PROGRESS;
+			vhost_set_used_len(vq, &used, VHOST_DMA_IN_PROGRESS);
+			vq->heads[nvq->upend_idx] = used;
 			ubuf->callback = vhost_zerocopy_callback;
 			ubuf->ctx = nvq->ubufs;
 			ubuf->desc = nvq->upend_idx;
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 641f4c6..af15bec 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2071,11 +2071,19 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 }
 EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
 
-static void vhost_set_used_len(struct vhost_virtqueue *vq,
-			       struct vhost_used_elem *used, int len)
+void vhost_set_used_len(struct vhost_virtqueue *vq,
+			struct vhost_used_elem *used, int len)
 {
 	used->elem.len = cpu_to_vhost32(vq, len);
 }
+EXPORT_SYMBOL_GPL(vhost_set_used_len);
+
+int vhost_get_used_len(struct vhost_virtqueue *vq,
+		       struct vhost_used_elem *used)
+{
+	return vhost32_to_cpu(vq, used->elem.len);
+}
+EXPORT_SYMBOL_GPL(vhost_get_used_len);
 
 /* This is a multi-buffer version of vhost_get_desc, that works if
  *	vq has read descriptors only.
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 8dea44b..604821b 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -198,6 +198,11 @@ int vhost_get_bufs(struct vhost_virtqueue *vq,
 		   unsigned *log_num,
 		   unsigned int quota,
 		   s16 *count);
+void vhost_set_used_len(struct vhost_virtqueue *vq,
+			struct vhost_used_elem *used,
+			int len);
+int vhost_get_used_len(struct vhost_virtqueue *vq,
+		       struct vhost_used_elem *used);
 void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
 
 int vhost_vq_init_access(struct vhost_virtqueue *);
-- 
2.7.4

[PATCH net-next V2 5/8] vhost: vhost_put_user() can accept metadata type

From: Jason Wang <hidden>
Date: 2018-07-16 03:28:55 

We assumes used ring update is the only user for vhost_put_user() in
the past. This may not be the case for the incoming packed ring which
may update the descriptor ring for used. So introduce a new type
parameter.

Signed-off-by: Jason Wang <redacted>
---
 drivers/vhost/vhost.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index af15bec..060a431 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -814,7 +814,7 @@ static inline void __user *__vhost_get_user(struct vhost_virtqueue *vq,
 	return __vhost_get_user_slow(vq, addr, size, type);
 }
 
-#define vhost_put_user(vq, x, ptr)		\
+#define vhost_put_user(vq, x, ptr, type)		\
 ({ \
 	int ret = -EFAULT; \
 	if (!vq->iotlb) { \
@@ -822,7 +822,7 @@ static inline void __user *__vhost_get_user(struct vhost_virtqueue *vq,
 	} else { \
 		__typeof__(ptr) to = \
 			(__typeof__(ptr)) __vhost_get_user(vq, ptr,	\
-					  sizeof(*ptr), VHOST_ADDR_USED); \
+					  sizeof(*ptr), type); \
 		if (to != NULL) \
 			ret = __put_user(x, to); \
 		else \
@@ -1687,7 +1687,7 @@ static int vhost_update_used_flags(struct vhost_virtqueue *vq)
 {
 	void __user *used;
 	if (vhost_put_user(vq, cpu_to_vhost16(vq, vq->used_flags),
-			   &vq->used->flags) < 0)
+			   &vq->used->flags, VHOST_ADDR_USED) < 0)
 		return -EFAULT;
 	if (unlikely(vq->log_used)) {
 		/* Make sure the flag is seen before log. */
@@ -1706,7 +1706,7 @@ static int vhost_update_used_flags(struct vhost_virtqueue *vq)
 static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
 {
 	if (vhost_put_user(vq, cpu_to_vhost16(vq, vq->avail_idx),
-			   vhost_avail_event(vq)))
+			   vhost_avail_event(vq), VHOST_ADDR_USED))
 		return -EFAULT;
 	if (unlikely(vq->log_used)) {
 		void __user *used;
@@ -2189,12 +2189,12 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,
 	used = vq->used->ring + start;
 	for (i = 0; i < count; i++) {
 		if (unlikely(vhost_put_user(vq, heads[i].elem.id,
-					    &used[i].id))) {
+					    &used[i].id, VHOST_ADDR_USED))) {
 			vq_err(vq, "Failed to write used id");
 			return -EFAULT;
 		}
 		if (unlikely(vhost_put_user(vq, heads[i].elem.len,
-					    &used[i].len))) {
+					    &used[i].len, VHOST_ADDR_USED))) {
 			vq_err(vq, "Failed to write used len");
 			return -EFAULT;
 		}
@@ -2240,7 +2240,7 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct vhost_used_elem *heads,
 	/* Make sure buffer is written before we update index. */
 	smp_wmb();
 	if (vhost_put_user(vq, cpu_to_vhost16(vq, vq->last_used_idx),
-			   &vq->used->idx)) {
+			   &vq->used->idx, VHOST_ADDR_USED)) {
 		vq_err(vq, "Failed to increment used idx");
 		return -EFAULT;
 	}
-- 
2.7.4

[PATCH net-next V2 6/8] vhost: packed ring support

From: Jason Wang <hidden>
Date: 2018-07-16 03:28:59 

This patch introduces basic support for packed ring. The idea behinds
packed ring is to use a single descriptor ring instead of three
different rings (avail, used and descriptor). This could help to
reduce the cache contention and PCI transactions. So it was designed
to help for the performance for both software implementation and
hardware implementation.

The implementation was straightforward, packed version of vhost core
(whose name has a packed suffix) helpers were introduced and previous
helpers were renamed with a split suffix. Then the exported helpers
can just do a switch to go to the correct internal helpers.

The event suppression (device area and driver area) were not
implemented. It will be done on top with another patch.

For more information of packed ring, please refer Virtio spec.

Signed-off-by: Jason Wang <redacted>
---
 drivers/vhost/net.c        |  12 +-
 drivers/vhost/vhost.c      | 653 ++++++++++++++++++++++++++++++++++++++++++---
 drivers/vhost/vhost.h      |  13 +-
 include/uapi/linux/vhost.h |   7 +
 4 files changed, 640 insertions(+), 45 deletions(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 2432002..77ec287 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -591,7 +591,7 @@ static void handle_tx(struct vhost_net *net)
 				nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
 					% UIO_MAXIOV;
 			}
-			vhost_discard_vq_desc(vq, 1);
+			vhost_discard_vq_desc(vq, &used, 1);
 			vhost_net_enable_vq(net, vq);
 			break;
 		}
@@ -755,10 +755,12 @@ static void handle_rx(struct vhost_net *net)
 
 	while ((sock_len = vhost_net_rx_peek_head_len(net, sock->sk,
 						      &busyloop_intr))) {
+		struct vhost_used_elem *used = vq->heads + nvq->done_idx;
+
 		sock_len += sock_hlen;
 		vhost_len = sock_len + vhost_hlen;
-		err = vhost_get_bufs(vq, vq->heads + nvq->done_idx,
-				     vhost_len, &in, vq_log, &log,
+		err = vhost_get_bufs(vq, used, vhost_len,
+				     &in, vq_log, &log,
 				     likely(mergeable) ? UIO_MAXIOV : 1,
 				     &headcount);
 		/* OK, now we need to know about added descriptors. */
@@ -806,7 +808,7 @@ static void handle_rx(struct vhost_net *net)
 		if (unlikely(err != sock_len)) {
 			pr_debug("Discarded rx packet: "
 				 " len %d, expected %zd\n", err, sock_len);
-			vhost_discard_vq_desc(vq, headcount);
+			vhost_discard_vq_desc(vq, used, 1);
 			continue;
 		}
 		/* Supply virtio_net_hdr if VHOST_NET_F_VIRTIO_NET_HDR */
@@ -830,7 +832,7 @@ static void handle_rx(struct vhost_net *net)
 		    copy_to_iter(&num_buffers, sizeof num_buffers,
 				 &fixup) != sizeof num_buffers) {
 			vq_err(vq, "Failed num_buffers write");
-			vhost_discard_vq_desc(vq, headcount);
+			vhost_discard_vq_desc(vq, used, 1);
 			goto out;
 		}
 		nvq->done_idx += headcount;
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 060a431..63b79e8 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -323,6 +323,9 @@ static void vhost_vq_reset(struct vhost_dev *dev,
 	vhost_reset_is_le(vq);
 	vhost_disable_cross_endian(vq);
 	vq->busyloop_timeout = 0;
+	vq->last_used_wrap_counter = true;
+	vq->last_avail_wrap_counter = true;
+	vq->avail_wrap_counter = true;
 	vq->umem = NULL;
 	vq->iotlb = NULL;
 	__vhost_vq_meta_reset(vq);
@@ -1106,11 +1109,22 @@ static int vhost_iotlb_miss(struct vhost_virtqueue *vq, u64 iova, int access)
 	return 0;
 }
 
-static bool vq_access_ok(struct vhost_virtqueue *vq, unsigned int num,
-			 struct vring_desc __user *desc,
-			 struct vring_avail __user *avail,
-			 struct vring_used __user *used)
+static int vq_access_ok_packed(struct vhost_virtqueue *vq, unsigned int num,
+			       struct vring_desc __user *desc,
+			       struct vring_avail __user *avail,
+			       struct vring_used __user *used)
+{
+	struct vring_packed_desc *packed = (struct vring_packed_desc *)desc;
+
+	/* TODO: check device area and driver area */
+	return access_ok(VERIFY_READ, packed, num * sizeof(*packed)) &&
+	       access_ok(VERIFY_WRITE, packed, num * sizeof(*packed));
+}
 
+static int vq_access_ok_split(struct vhost_virtqueue *vq, unsigned int num,
+			      struct vring_desc __user *desc,
+			      struct vring_avail __user *avail,
+			      struct vring_used __user *used)
 {
 	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 
@@ -1121,6 +1135,17 @@ static bool vq_access_ok(struct vhost_virtqueue *vq, unsigned int num,
 			sizeof *used + num * sizeof *used->ring + s);
 }
 
+static int vq_access_ok(struct vhost_virtqueue *vq, unsigned int num,
+			struct vring_desc __user *desc,
+			struct vring_avail __user *avail,
+			struct vring_used __user *used)
+{
+	if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+		return vq_access_ok_packed(vq, num, desc, avail, used);
+	else
+		return vq_access_ok_split(vq, num, desc, avail, used);
+}
+
 static void vhost_vq_meta_update(struct vhost_virtqueue *vq,
 				 const struct vhost_umem_node *node,
 				 int type)
@@ -1318,6 +1343,7 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
 	struct vhost_vring_state s;
 	struct vhost_vring_file f;
 	struct vhost_vring_addr a;
+	bool wrap_counter;
 	u32 idx;
 	long r;
 
@@ -1360,6 +1386,10 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
 			r = -EFAULT;
 			break;
 		}
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			wrap_counter = s.num >> 31;
+			s.num &= ~(1 << 31);
+		}
 		if (s.num > 0xffff) {
 			r = -EINVAL;
 			break;
@@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
 		vq->last_avail_idx = s.num;
 		/* Forget the cached index value. */
 		vq->avail_idx = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			vq->last_avail_wrap_counter = wrap_counter;
+			vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+		}
 		break;
 	case VHOST_GET_VRING_BASE:
 		s.index = idx;
 		s.num = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_avail_wrap_counter << 31;
+		if (copy_to_user(argp, &s, sizeof(s)))
+			r = -EFAULT;
+		break;
+	case VHOST_SET_VRING_USED_BASE:
+		/* Moving base with an active backend?
+		 * You don't want to do that.
+		 */
+		if (vq->private_data) {
+			r = -EBUSY;
+			break;
+		}
+		if (copy_from_user(&s, argp, sizeof(s))) {
+			r = -EFAULT;
+			break;
+		}
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			wrap_counter = s.num >> 31;
+			s.num &= ~(1 << 31);
+		}
+		if (s.num > 0xffff) {
+			r = -EINVAL;
+			break;
+		}
+		vq->last_used_idx = s.num;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			vq->last_used_wrap_counter = wrap_counter;
+		break;
+	case VHOST_GET_VRING_USED_BASE:
+		s.index = idx;
+		s.num = vq->last_used_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_used_wrap_counter << 31;
 		if (copy_to_user(argp, &s, sizeof s))
 			r = -EFAULT;
 		break;
@@ -1734,6 +1802,9 @@ int vhost_vq_init_access(struct vhost_virtqueue *vq)
 
 	vhost_init_is_le(vq);
 
+	if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+		return 0;
+
 	r = vhost_update_used_flags(vq);
 	if (r)
 		goto err;
@@ -1807,7 +1878,8 @@ static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
 /* Each buffer in the virtqueues is actually a chain of descriptors.  This
  * function returns the next descriptor in the chain,
  * or -1U if we're at the end. */
-static unsigned next_desc(struct vhost_virtqueue *vq, struct vring_desc *desc)
+static unsigned next_desc_split(struct vhost_virtqueue *vq,
+				struct vring_desc *desc)
 {
 	unsigned int next;
 
@@ -1820,11 +1892,17 @@ static unsigned next_desc(struct vhost_virtqueue *vq, struct vring_desc *desc)
 	return next;
 }
 
-static int get_indirect(struct vhost_virtqueue *vq,
-			struct iovec iov[], unsigned int iov_size,
-			unsigned int *out_num, unsigned int *in_num,
-			struct vhost_log *log, unsigned int *log_num,
-			struct vring_desc *indirect)
+static unsigned next_desc_packed(struct vhost_virtqueue *vq,
+				 struct vring_packed_desc *desc)
+{
+	return desc->flags & cpu_to_vhost16(vq, VRING_DESC_F_NEXT);
+}
+
+static int get_indirect_split(struct vhost_virtqueue *vq,
+			      struct iovec iov[], unsigned int iov_size,
+			      unsigned int *out_num, unsigned int *in_num,
+			      struct vhost_log *log, unsigned int *log_num,
+			      struct vring_desc *indirect)
 {
 	struct vring_desc desc;
 	unsigned int i = 0, count, found = 0;
@@ -1914,23 +1992,298 @@ static int get_indirect(struct vhost_virtqueue *vq,
 			}
 			*out_num += ret;
 		}
-	} while ((i = next_desc(vq, &desc)) != -1);
+	} while ((i = next_desc_split(vq, &desc)) != -1);
 	return 0;
 }
 
-/* This looks in the virtqueue and for the first available buffer, and converts
- * it to an iovec for convenient access.  Since descriptors consist of some
- * number of output then some number of input descriptors, it's actually two
- * iovecs, but we pack them into one and note how many of each there were.
- *
- * This function returns the descriptor number found, or vq->num (which is
- * never a valid descriptor number) if none was found.  A negative code is
- * returned on error. */
-int vhost_get_vq_desc(struct vhost_virtqueue *vq,
-		      struct vhost_used_elem *used,
-		      struct iovec iov[], unsigned int iov_size,
-		      unsigned int *out_num, unsigned int *in_num,
-		      struct vhost_log *log, unsigned int *log_num)
+static int get_indirect_packed(struct vhost_virtqueue *vq,
+			       struct iovec iov[], unsigned int iov_size,
+			       unsigned int *out_num, unsigned int *in_num,
+			       struct vhost_log *log, unsigned int *log_num,
+			       struct vring_packed_desc *indirect)
+{
+	struct vring_packed_desc desc;
+	unsigned int i = 0, count, found = 0;
+	u32 len = vhost32_to_cpu(vq, indirect->len);
+	struct iov_iter from;
+	int ret, access;
+
+	/* Sanity check */
+	if (unlikely(len % sizeof(desc))) {
+		vq_err(vq, "Invalid length in indirect descriptor: len 0x%llx not multiple of 0x%zx\n",
+		       (unsigned long long)len,
+		       sizeof(desc));
+		return -EINVAL;
+	}
+
+	ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr),
+			     len, vq->indirect,
+			     UIO_MAXIOV, VHOST_ACCESS_RO);
+	if (unlikely(ret < 0)) {
+		if (ret != -EAGAIN)
+			vq_err(vq, "Translation failure %d in indirect.\n",
+			       ret);
+		return ret;
+	}
+	iov_iter_init(&from, READ, vq->indirect, ret, len);
+
+	/* We will use the result as an address to read from, so most
+	 * architectures only need a compiler barrier here.
+	 */
+	read_barrier_depends();
+
+	count = len / sizeof(desc);
+	/* Buffers are chained via a 16 bit next field, so
+	 * we can have at most 2^16 of these.
+	 */
+	if (unlikely(count > USHRT_MAX + 1)) {
+		vq_err(vq, "Indirect buffer length too big: %d\n",
+		       indirect->len);
+		return -E2BIG;
+	}
+
+	do {
+		unsigned int iov_count = *in_num + *out_num;
+
+		if (unlikely(++found > count)) {
+			vq_err(vq, "Loop detected: last one at %u indirect size %u\n",
+			       i, count);
+			return -EINVAL;
+		}
+		if (unlikely(!copy_from_iter_full(&desc, sizeof(desc),
+						  &from))) {
+			vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
+			       i, (size_t)vhost64_to_cpu(vq, indirect->addr)
+				  + i * sizeof(desc));
+			return -EINVAL;
+		}
+		if (unlikely(desc.flags &
+			     cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT))) {
+			vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
+			       i, (size_t)vhost64_to_cpu(vq, indirect->addr)
+				  + i * sizeof(desc));
+			return -EINVAL;
+		}
+
+		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE))
+			access = VHOST_ACCESS_WO;
+		else
+			access = VHOST_ACCESS_RO;
+
+		ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
+				     vhost32_to_cpu(vq, desc.len),
+				     iov + iov_count,
+				     iov_size - iov_count, access);
+		if (unlikely(ret < 0)) {
+			if (ret != -EAGAIN)
+				vq_err(vq, "Translation failure %d indirect idx %d\n",
+				       ret, i);
+			return ret;
+		}
+		/* If this is an input descriptor, increment that count. */
+		if (access == VHOST_ACCESS_WO) {
+			*in_num += ret;
+			if (unlikely(log)) {
+				log[*log_num].addr =
+					vhost64_to_cpu(vq, desc.addr);
+				log[*log_num].len =
+					vhost32_to_cpu(vq, desc.len);
+				++*log_num;
+			}
+		} else {
+			/* If it's an output descriptor, they're all supposed
+			 * to come before any input descriptors.
+			 */
+			if (unlikely(*in_num)) {
+				vq_err(vq, "Indirect descriptor has out after in: idx %d\n",
+				       i);
+				return -EINVAL;
+			}
+			*out_num += ret;
+		}
+		i++;
+	} while (next_desc_packed(vq, &desc));
+	return 0;
+}
+
+static bool desc_is_avail(struct vhost_virtqueue *vq, bool wrap_counter,
+			  __virtio16 flags)
+{
+	bool avail = flags & cpu_to_vhost16(vq, VRING_DESC_F_AVAIL);
+
+	return avail == wrap_counter;
+}
+
+static __virtio16 get_desc_flags(struct vhost_virtqueue *vq,
+				 bool wrap_counter, bool write)
+{
+	__virtio16 flags = 0;
+
+	if (wrap_counter) {
+		flags |= cpu_to_vhost16(vq, VRING_DESC_F_AVAIL);
+		flags |= cpu_to_vhost16(vq, VRING_DESC_F_USED);
+	} else {
+		flags &= ~cpu_to_vhost16(vq, VRING_DESC_F_AVAIL);
+		flags &= ~cpu_to_vhost16(vq, VRING_DESC_F_USED);
+	}
+
+	if (write)
+		flags |= cpu_to_vhost16(vq, VRING_DESC_F_WRITE);
+
+	return flags;
+}
+
+static bool vhost_vring_packed_need_event(struct vhost_virtqueue *vq,
+					  bool wrap, __u16 off_wrap, __u16 new,
+					  __u16 old)
+{
+	int off = off_wrap & ~(1 << 15);
+
+	if (wrap != off_wrap >> 15)
+		off -= vq->num;
+
+	return vring_need_event(off, new, old);
+}
+
+static int vhost_get_vq_desc_packed(struct vhost_virtqueue *vq,
+				    struct vhost_used_elem *used,
+				    struct iovec iov[], unsigned int iov_size,
+				    unsigned int *out_num, unsigned int *in_num,
+				    struct vhost_log *log,
+				    unsigned int *log_num)
+{
+	struct vring_packed_desc desc;
+	int ret, access, i;
+	u16 last_avail_idx = vq->last_avail_idx;
+	u16 off_wrap = vq->avail_idx | (vq->avail_wrap_counter << 15);
+
+	/* When we start there are none of either input nor output. */
+	*out_num = *in_num = 0;
+	if (unlikely(log))
+		*log_num = 0;
+
+	used->count = 0;
+
+	do {
+		struct vring_packed_desc *d = vq->desc_packed +
+					      vq->last_avail_idx;
+		unsigned int iov_count = *in_num + *out_num;
+
+		ret = vhost_get_user(vq, desc.flags, &d->flags,
+				     VHOST_ADDR_DESC);
+		if (unlikely(ret)) {
+			vq_err(vq, "Failed to get flags: idx %d addr %p\n",
+			       vq->last_avail_idx, &d->flags);
+			return -EFAULT;
+		}
+
+		if (!desc_is_avail(vq, vq->last_avail_wrap_counter,
+				   desc.flags)) {
+			/* If there's nothing new since last we looked, return
+			 * invalid.
+			 */
+			if (!used->count)
+				return -ENOSPC;
+			vq_err(vq, "Unexpected unavail descriptor: idx %d\n",
+			       vq->last_avail_idx);
+			return -EFAULT;
+		}
+
+		/* Read desc content after we're sure it was available. */
+		smp_rmb();
+
+		ret = vhost_copy_from_user(vq, &desc, d, sizeof(desc));
+		if (unlikely(ret)) {
+			vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
+				vq->last_avail_idx, d);
+			return -EFAULT;
+		}
+
+		used->elem.id = desc.id;
+
+		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT)) {
+			ret = get_indirect_packed(vq, iov, iov_size,
+						  out_num, in_num, log,
+						  log_num, &desc);
+			if (unlikely(ret < 0)) {
+				if (ret != -EAGAIN)
+					vq_err(vq, "Failure detected in indirect descriptor at idx %d\n",
+					       i);
+				return ret;
+			}
+			goto next;
+		}
+
+		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE))
+			access = VHOST_ACCESS_WO;
+		else
+			access = VHOST_ACCESS_RO;
+		ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
+				     vhost32_to_cpu(vq, desc.len),
+				     iov + iov_count, iov_size - iov_count,
+				     access);
+		if (unlikely(ret < 0)) {
+			if (ret != -EAGAIN)
+				vq_err(vq, "Translation failure %d idx %d\n",
+				       ret, i);
+			return ret;
+		}
+
+		if (access == VHOST_ACCESS_WO) {
+			/* If this is an input descriptor,
+			 * increment that count.
+			 */
+			*in_num += ret;
+			if (unlikely(log)) {
+				log[*log_num].addr =
+					vhost64_to_cpu(vq, desc.addr);
+				log[*log_num].len =
+					vhost32_to_cpu(vq, desc.len);
+				++*log_num;
+			}
+		} else {
+			/* If it's an output descriptor, they're all supposed
+			 * to come before any input descriptors.
+			 */
+			if (unlikely(*in_num)) {
+				vq_err(vq, "Desc out after in: idx %d\n", i);
+				return -EINVAL;
+			}
+			*out_num += ret;
+		}
+
+next:
+		if (unlikely(++used->count > vq->num)) {
+			vq_err(vq, "Loop detected: last one at %u vq size %u head %u\n",
+			       i, vq->num, used->elem.id);
+			return -EINVAL;
+		}
+		if (++vq->last_avail_idx >= vq->num) {
+			vq->last_avail_idx = 0;
+			vq->last_avail_wrap_counter ^= 1;
+		}
+	/* If this descriptor says it doesn't chain, we're done. */
+	} while (next_desc_packed(vq, &desc));
+
+	/* Packed ring does not have avail idx which means we need to
+	 * track it by our own. The check here is to make sure it
+	 * grows monotonically.
+	 */
+	if (vhost_vring_packed_need_event(vq, vq->last_avail_wrap_counter,
+					  off_wrap, vq->last_avail_idx,
+					  last_avail_idx)) {
+		vq->avail_idx = vq->last_avail_idx;
+		vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+	}
+
+	return 0;
+}
+
+static int vhost_get_vq_desc_split(struct vhost_virtqueue *vq,
+				   struct vhost_used_elem *used,
+				   struct iovec iov[], unsigned int iov_size,
+				   unsigned int *out_num, unsigned int *in_num,
+				   struct vhost_log *log, unsigned int *log_num)
 {
 	struct vring_desc desc;
 	unsigned int i, head, found = 0;
@@ -2015,9 +2368,9 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 			return -EFAULT;
 		}
 		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT)) {
-			ret = get_indirect(vq, iov, iov_size,
-					   out_num, in_num,
-					   log, log_num, &desc);
+			ret = get_indirect_split(vq, iov, iov_size,
+						 out_num, in_num,
+						 log, log_num, &desc);
 			if (unlikely(ret < 0)) {
 				if (ret != -EAGAIN)
 					vq_err(vq, "Failure detected "
@@ -2059,7 +2412,7 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 			}
 			*out_num += ret;
 		}
-	} while ((i = next_desc(vq, &desc)) != -1);
+	} while ((i = next_desc_split(vq, &desc)) != -1);
 
 	/* On success, increment avail index. */
 	vq->last_avail_idx++;
@@ -2069,6 +2422,31 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 	BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
 	return 0;
 }
+
+/* This looks in the virtqueue and for the first available buffer, and converts
+ * it to an iovec for convenient access.  Since descriptors consist of some
+ * number of output then some number of input descriptors, it's actually two
+ * iovecs, but we pack them into one and note how many of each there were.
+ *
+ * This function returns the descriptor number found, or vq->num (which is
+ * never a valid descriptor number) if none was found.  A negative code is
+ * returned on error.
+ */
+int vhost_get_vq_desc(struct vhost_virtqueue *vq,
+		      struct vhost_used_elem *used,
+		      struct iovec iov[], unsigned int iov_size,
+		      unsigned int *out_num, unsigned int *in_num,
+		      struct vhost_log *log, unsigned int *log_num)
+{
+	if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+		return vhost_get_vq_desc_packed(vq, used, iov, iov_size,
+						out_num, in_num,
+						log, log_num);
+	else
+		return vhost_get_vq_desc_split(vq, used, iov, iov_size,
+					       out_num, in_num,
+					       log, log_num);
+}
 EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
 
 void vhost_set_used_len(struct vhost_virtqueue *vq,
@@ -2155,15 +2533,30 @@ int vhost_get_bufs(struct vhost_virtqueue *vq,
 	*count = headcount;
 	return 0;
 err:
-	vhost_discard_vq_desc(vq, headcount);
+	vhost_discard_vq_desc(vq, heads, headcount);
 	return r;
 }
 EXPORT_SYMBOL_GPL(vhost_get_bufs);
 
 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
-void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
+void vhost_discard_vq_desc(struct vhost_virtqueue *vq,
+			   struct vhost_used_elem *heads,
+			   int headcount)
 {
-	vq->last_avail_idx -= n;
+	int i;
+
+	if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+		for (i = 0; i < headcount; i++) {
+			vq->last_avail_idx -= heads[i].count;
+			if (vq->last_avail_idx >= vq->num) {
+				vq->last_avail_wrap_counter ^= 1;
+				vq->last_avail_idx += vq->num;
+			}
+		}
+	} else {
+		vq->last_avail_idx -= headcount;
+	}
+
 }
 EXPORT_SYMBOL_GPL(vhost_discard_vq_desc);
 
@@ -2219,10 +2612,102 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,
 	return 0;
 }
 
+static int vhost_add_used_packed(struct vhost_virtqueue *vq,
+				 struct vhost_used_elem *used,
+				 int idx, bool wrap_counter)
+{
+	struct vring_packed_desc __user *desc = vq->desc_packed + idx;
+	int ret;
+
+	ret = vhost_put_user(vq, used->elem.id, &desc->id, VHOST_ADDR_DESC);
+	if (unlikely(ret)) {
+		vq_err(vq, "Failed to update id: idx %d addr %p\n",
+		       vq->last_used_idx, desc);
+		return -EFAULT;
+	}
+	ret = vhost_put_user(vq, used->elem.len, &desc->len, VHOST_ADDR_DESC);
+	if (unlikely(ret)) {
+		vq_err(vq, "Failed to update len: idx %d addr %p\n",
+		       vq->last_used_idx, desc);
+		return -EFAULT;
+	}
+
+	if (idx == vq->last_used_idx) {
+		/* Make sure descriptor id and len is written before
+		 * flags for the first used buffer.
+		 */
+		smp_wmb();
+	}
+
+	ret = vhost_put_user(vq,
+			     get_desc_flags(vq, wrap_counter, used->elem.len),
+			     &desc->flags, VHOST_ADDR_DESC);
+	if (unlikely(ret)) {
+		vq_err(vq, "Failed to update flags: idx %d addr %p\n",
+		       vq->last_used_idx, desc);
+		return -EFAULT;
+	}
+
+	if (unlikely(vq->log_used)) {
+		/* Make sure desc is written before update log. */
+		smp_wmb();
+		log_write(vq->log_base, vq->log_addr +
+			  vq->last_used_idx * sizeof(*desc),
+			  sizeof(*desc));
+		if (vq->log_ctx)
+			eventfd_signal(vq->log_ctx, 1);
+	}
+
+	return 0;
+}
+
+static int vhost_add_used_n_packed(struct vhost_virtqueue *vq,
+				   struct vhost_used_elem *heads,
+				   unsigned int count)
+{
+	u16 last_used_idx = vq->last_used_idx + heads[0].count;
+	u16 wrap_counter = vq->last_used_wrap_counter;
+	int i, ret;
+
+	/* Update used elems other than first to save unnecessary
+	 * memory barriers.
+	 */
+	for (i = 1; i < count; i++) {
+		if (last_used_idx >= vq->num) {
+			last_used_idx -= vq->num;
+			wrap_counter ^= 1;
+		}
+
+		ret = vhost_add_used_packed(vq, &heads[i], last_used_idx,
+					    wrap_counter);
+		if (unlikely(ret))
+			return ret;
+
+		last_used_idx += heads[i].count;
+	}
+
+	ret = vhost_add_used_packed(vq, &heads[0], vq->last_used_idx,
+				    vq->last_used_wrap_counter);
+	if (unlikely(ret))
+		return ret;
+
+	if (last_used_idx >= vq->num) {
+		last_used_idx -= vq->num;
+		wrap_counter ^= 1;
+	}
+
+	vq->last_used_idx = last_used_idx;
+	vq->last_used_wrap_counter = wrap_counter;
+
+	return 0;
+}
+
 /* After we've used one of their buffers, we tell them about it.  We'll then
  * want to notify the guest, using eventfd. */
-int vhost_add_used_n(struct vhost_virtqueue *vq, struct vhost_used_elem *heads,
-		     unsigned count)
+static int vhost_add_used_n_split(struct vhost_virtqueue *vq,
+				  struct vhost_used_elem *heads,
+				  unsigned count)
+
 {
 	int start, n, r;
 
@@ -2254,6 +2739,19 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct vhost_used_elem *heads,
 	}
 	return r;
 }
+
+/* After we've used one of their buffers, we tell them about it.  We'll then
+ * want to notify the guest, using eventfd.
+ */
+int vhost_add_used_n(struct vhost_virtqueue *vq,
+		     struct vhost_used_elem *heads,
+		     unsigned int count)
+{
+	if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+		return vhost_add_used_n_packed(vq, heads, count);
+	else
+		return vhost_add_used_n_split(vq, heads, count);
+}
 EXPORT_SYMBOL_GPL(vhost_add_used_n);
 
 static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
@@ -2261,6 +2759,11 @@ static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
 	__u16 old, new;
 	__virtio16 event;
 	bool v;
+
+	/* TODO: check driver area */
+	if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+		return true;
+
 	/* Flush out used index updates. This is paired
 	 * with the barrier that the Guest executes when enabling
 	 * interrupts. */
@@ -2323,7 +2826,8 @@ void vhost_add_used_and_signal_n(struct vhost_dev *dev,
 EXPORT_SYMBOL_GPL(vhost_add_used_and_signal_n);
 
 /* return true if we're sure that avaiable ring is empty */
-bool vhost_vq_avail_empty(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+static bool vhost_vq_avail_empty_split(struct vhost_dev *dev,
+				       struct vhost_virtqueue *vq)
 {
 	__virtio16 avail_idx;
 	int r;
@@ -2338,10 +2842,59 @@ bool vhost_vq_avail_empty(struct vhost_dev *dev, struct vhost_virtqueue *vq)
 
 	return vq->avail_idx == vq->last_avail_idx;
 }
+
+static bool vhost_vq_avail_empty_packed(struct vhost_dev *dev,
+					struct vhost_virtqueue *vq)
+{
+	struct vring_packed_desc *d = vq->desc_packed + vq->avail_idx;
+	__virtio16 flags;
+	int ret;
+
+	ret = vhost_get_user(vq, flags, &d->flags, VHOST_ADDR_DESC);
+	if (unlikely(ret)) {
+		vq_err(vq, "Failed to get flags: idx %d addr %p\n",
+			vq->last_avail_idx, d);
+		return -EFAULT;
+	}
+
+	return !desc_is_avail(vq, vq->avail_wrap_counter, flags);
+}
+
+bool vhost_vq_avail_empty(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+{
+	if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+		return vhost_vq_avail_empty_packed(dev, vq);
+	else
+		return vhost_vq_avail_empty_split(dev, vq);
+}
 EXPORT_SYMBOL_GPL(vhost_vq_avail_empty);
 
-/* OK, now we need to know about added descriptors. */
-bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+static bool vhost_enable_notify_packed(struct vhost_dev *dev,
+				       struct vhost_virtqueue *vq)
+{
+	struct vring_packed_desc *d = vq->desc_packed + vq->avail_idx;
+	__virtio16 flags;
+	int ret;
+
+	/* TODO: enable notification through device area */
+
+	/* They could have slipped one in as we were doing that: make
+	 * sure it's written, then check again.
+	 */
+	smp_mb();
+
+	ret = vhost_get_user(vq, flags, &d->flags, VHOST_ADDR_DESC);
+	if (unlikely(ret)) {
+		vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
+			vq->last_avail_idx, &d->flags);
+		return -EFAULT;
+	}
+
+	return desc_is_avail(vq, vq->avail_wrap_counter, flags);
+}
+
+static bool vhost_enable_notify_split(struct vhost_dev *dev,
+				      struct vhost_virtqueue *vq)
 {
 	__virtio16 avail_idx;
 	int r;
@@ -2376,10 +2929,25 @@ bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
 
 	return vhost16_to_cpu(vq, avail_idx) != vq->avail_idx;
 }
+
+/* OK, now we need to know about added descriptors. */
+bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+{
+	if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+		return vhost_enable_notify_packed(dev, vq);
+	else
+		return vhost_enable_notify_split(dev, vq);
+}
 EXPORT_SYMBOL_GPL(vhost_enable_notify);
 
-/* We don't need to be notified again. */
-void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+static void vhost_disable_notify_packed(struct vhost_dev *dev,
+					struct vhost_virtqueue *vq)
+{
+	/* TODO: disable notification through device area */
+}
+
+static void vhost_disable_notify_split(struct vhost_dev *dev,
+				       struct vhost_virtqueue *vq)
 {
 	int r;
 
@@ -2393,6 +2961,15 @@ void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
 			       &vq->used->flags, r);
 	}
 }
+
+/* We don't need to be notified again. */
+void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+{
+	if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+		return vhost_disable_notify_packed(dev, vq);
+	else
+		return vhost_disable_notify_split(dev, vq);
+}
 EXPORT_SYMBOL_GPL(vhost_disable_notify);
 
 /* Create a new message. */
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 604821b..73c2a78 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -36,6 +36,7 @@ struct vhost_poll {
 
 struct vhost_used_elem {
 	struct vring_used_elem elem;
+	int count;
 };
 
 void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn);
@@ -91,7 +92,10 @@ struct vhost_virtqueue {
 	/* The actual ring of buffers. */
 	struct mutex mutex;
 	unsigned int num;
-	struct vring_desc __user *desc;
+	union {
+		struct vring_desc __user *desc;
+		struct vring_packed_desc __user *desc_packed;
+	};
 	struct vring_avail __user *avail;
 	struct vring_used __user *used;
 	const struct vhost_umem_node *meta_iotlb[VHOST_NUM_ADDRS];
@@ -148,6 +152,9 @@ struct vhost_virtqueue {
 	bool user_be;
 #endif
 	u32 busyloop_timeout;
+	bool last_used_wrap_counter;
+	bool avail_wrap_counter;
+	bool last_avail_wrap_counter;
 };
 
 struct vhost_msg_node {
@@ -203,7 +210,9 @@ void vhost_set_used_len(struct vhost_virtqueue *vq,
 			int len);
 int vhost_get_used_len(struct vhost_virtqueue *vq,
 		       struct vhost_used_elem *used);
-void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
+void vhost_discard_vq_desc(struct vhost_virtqueue *vq,
+			   struct vhost_used_elem *elem,
+			   int n);
 
 int vhost_vq_init_access(struct vhost_virtqueue *);
 int vhost_add_used(struct vhost_virtqueue *vq,
diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
index c51f8e5..839ae7e 100644
--- a/include/uapi/linux/vhost.h
+++ b/include/uapi/linux/vhost.h
@@ -160,6 +160,13 @@ struct vhost_memory {
 #define VHOST_GET_VRING_BUSYLOOP_TIMEOUT _IOW(VHOST_VIRTIO, 0x24,	\
 					 struct vhost_vring_state)
 
+/* Base value where queue looks for used descriptors */
+#define VHOST_SET_VRING_USED_BASE _IOW(VHOST_VIRTIO, 0x25,	\
+				  struct vhost_vring_state)
+/* Get accessor: reads index, writes value in num */
+#define VHOST_GET_VRING_USED_BASE _IOWR(VHOST_VIRTIO, 0x26,	\
+				  struct vhost_vring_state)
+
 /* VHOST_NET specific defines */
 
 /* Attach virtio net ring to a raw socket, or tap device.
-- 
2.7.4

[PATCH net-next V2 7/8] vhost: event suppression for packed ring

From: Jason Wang <hidden>
Date: 2018-07-16 03:29:04 

This patch introduces support for event suppression. This is done by
have a two areas: device area and driver area. One side could then try
to disable or enable (delayed) notification from other side by using a
boolean hint or event index interface in the areas.

For more information, please refer Virtio spec.

Signed-off-by: Jason Wang <redacted>
---
 drivers/vhost/vhost.c | 191 ++++++++++++++++++++++++++++++++++++++++++++++----
 drivers/vhost/vhost.h |  10 ++-
 2 files changed, 185 insertions(+), 16 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 63b79e8..0459f8b 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1115,10 +1115,15 @@ static int vq_access_ok_packed(struct vhost_virtqueue *vq, unsigned int num,
 			       struct vring_used __user *used)
 {
 	struct vring_packed_desc *packed = (struct vring_packed_desc *)desc;
+	struct vring_packed_desc_event *driver_event =
+		(struct vring_packed_desc_event *)avail;
+	struct vring_packed_desc_event *device_event =
+		(struct vring_packed_desc_event *)used;
 
-	/* TODO: check device area and driver area */
 	return access_ok(VERIFY_READ, packed, num * sizeof(*packed)) &&
-	       access_ok(VERIFY_WRITE, packed, num * sizeof(*packed));
+	       access_ok(VERIFY_WRITE, packed, num * sizeof(*packed)) &&
+	       access_ok(VERIFY_READ, driver_event, sizeof(*driver_event)) &&
+	       access_ok(VERIFY_WRITE, device_event, sizeof(*device_event));
 }
 
 static int vq_access_ok_split(struct vhost_virtqueue *vq, unsigned int num,
@@ -1193,14 +1198,27 @@ static bool iotlb_access_ok(struct vhost_virtqueue *vq,
 	return true;
 }
 
-int vq_iotlb_prefetch(struct vhost_virtqueue *vq)
+int vq_iotlb_prefetch_packed(struct vhost_virtqueue *vq)
+{
+	int num = vq->num;
+
+	return iotlb_access_ok(vq, VHOST_ACCESS_RO, (u64)(uintptr_t)vq->desc,
+			       num * sizeof(*vq->desc), VHOST_ADDR_DESC) &&
+	       iotlb_access_ok(vq, VHOST_ACCESS_WO, (u64)(uintptr_t)vq->desc,
+			       num * sizeof(*vq->desc), VHOST_ADDR_DESC) &&
+	       iotlb_access_ok(vq, VHOST_ACCESS_RO,
+			       (u64)(uintptr_t)vq->driver_event,
+			       sizeof(*vq->driver_event), VHOST_ADDR_AVAIL) &&
+	       iotlb_access_ok(vq, VHOST_ACCESS_WO,
+			       (u64)(uintptr_t)vq->device_event,
+			       sizeof(*vq->device_event), VHOST_ADDR_USED);
+}
+
+int vq_iotlb_prefetch_split(struct vhost_virtqueue *vq)
 {
 	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
 	unsigned int num = vq->num;
 
-	if (!vq->iotlb)
-		return 1;
-
 	return iotlb_access_ok(vq, VHOST_ACCESS_RO, (u64)(uintptr_t)vq->desc,
 			       num * sizeof(*vq->desc), VHOST_ADDR_DESC) &&
 	       iotlb_access_ok(vq, VHOST_ACCESS_RO, (u64)(uintptr_t)vq->avail,
@@ -1212,6 +1230,17 @@ int vq_iotlb_prefetch(struct vhost_virtqueue *vq)
 			       num * sizeof(*vq->used->ring) + s,
 			       VHOST_ADDR_USED);
 }
+
+int vq_iotlb_prefetch(struct vhost_virtqueue *vq)
+{
+	if (!vq->iotlb)
+		return 1;
+
+	if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+		return vq_iotlb_prefetch_packed(vq);
+	else
+		return vq_iotlb_prefetch_split(vq);
+}
 EXPORT_SYMBOL_GPL(vq_iotlb_prefetch);
 
 /* Can we log writes? */
@@ -1771,6 +1800,50 @@ static int vhost_update_used_flags(struct vhost_virtqueue *vq)
 	return 0;
 }
 
+static int vhost_update_device_flags(struct vhost_virtqueue *vq,
+				     __virtio16 device_flags)
+{
+	void __user *flags;
+
+	if (vhost_put_user(vq, device_flags, &vq->device_event->flags,
+			   VHOST_ADDR_USED) < 0)
+		return -EFAULT;
+	if (unlikely(vq->log_used)) {
+		/* Make sure the flag is seen before log. */
+		smp_wmb();
+		/* Log used flag write. */
+		flags = &vq->device_event->flags;
+		log_write(vq->log_base, vq->log_addr +
+			  (flags - (void __user *)vq->device_event),
+			  sizeof(vq->device_event->flags));
+		if (vq->log_ctx)
+			eventfd_signal(vq->log_ctx, 1);
+	}
+	return 0;
+}
+
+static int vhost_update_device_off_wrap(struct vhost_virtqueue *vq,
+					__virtio16 device_off_wrap)
+{
+	void __user *off_wrap;
+
+	if (vhost_put_user(vq, device_off_wrap, &vq->device_event->off_wrap,
+			   VHOST_ADDR_USED) < 0)
+		return -EFAULT;
+	if (unlikely(vq->log_used)) {
+		/* Make sure the flag is seen before log. */
+		smp_wmb();
+		/* Log used flag write. */
+		off_wrap = &vq->device_event->off_wrap;
+		log_write(vq->log_base, vq->log_addr +
+			  (off_wrap - (void __user *)vq->device_event),
+			  sizeof(vq->device_event->off_wrap));
+		if (vq->log_ctx)
+			eventfd_signal(vq->log_ctx, 1);
+	}
+	return 0;
+}
+
 static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
 {
 	if (vhost_put_user(vq, cpu_to_vhost16(vq, vq->avail_idx),
@@ -2754,16 +2827,13 @@ int vhost_add_used_n(struct vhost_virtqueue *vq,
 }
 EXPORT_SYMBOL_GPL(vhost_add_used_n);
 
-static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+static bool vhost_notify_split(struct vhost_dev *dev,
+			       struct vhost_virtqueue *vq)
 {
 	__u16 old, new;
 	__virtio16 event;
 	bool v;
 
-	/* TODO: check driver area */
-	if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
-		return true;
-
 	/* Flush out used index updates. This is paired
 	 * with the barrier that the Guest executes when enabling
 	 * interrupts. */
@@ -2796,6 +2866,64 @@ static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
 	return vring_need_event(vhost16_to_cpu(vq, event), new, old);
 }
 
+static bool vhost_notify_packed(struct vhost_dev *dev,
+				struct vhost_virtqueue *vq)
+{
+	__virtio16 event_off_wrap, event_flags;
+	__u16 old, new, off_wrap;
+	bool v;
+
+	/* Flush out used descriptors updates. This is paired
+	 * with the barrier that the Guest executes when enabling
+	 * interrupts.
+	 */
+	smp_mb();
+
+	if (vhost_get_avail(vq, event_flags,
+			   &vq->driver_event->flags) < 0) {
+		vq_err(vq, "Failed to get driver desc_event_flags");
+		return true;
+	}
+
+	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX))
+		return event_flags !=
+		       cpu_to_vhost16(vq, VRING_EVENT_F_DISABLE);
+
+	old = vq->signalled_used;
+	v = vq->signalled_used_valid;
+	new = vq->signalled_used = vq->last_used_idx;
+	vq->signalled_used_valid = true;
+
+	if (event_flags != cpu_to_vhost16(vq, VRING_EVENT_F_DESC))
+		return event_flags !=
+		       cpu_to_vhost16(vq, VRING_EVENT_F_DISABLE);
+
+	/* Read desc event flags before event_off and event_wrap */
+	smp_rmb();
+
+	if (vhost_get_avail(vq, event_off_wrap,
+			    &vq->driver_event->off_wrap) < 0) {
+		vq_err(vq, "Failed to get driver desc_event_off/wrap");
+		return true;
+	}
+
+	off_wrap = vhost16_to_cpu(vq, event_off_wrap);
+
+	if (unlikely(!v))
+		return true;
+
+	return vhost_vring_packed_need_event(vq, vq->last_used_wrap_counter,
+					     off_wrap, new, old);
+}
+
+static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+{
+	if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+		return vhost_notify_packed(dev, vq);
+	else
+		return vhost_notify_split(dev, vq);
+}
+
 /* This actually signals the guest, using eventfd. */
 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
 {
@@ -2873,10 +3001,34 @@ static bool vhost_enable_notify_packed(struct vhost_dev *dev,
 				       struct vhost_virtqueue *vq)
 {
 	struct vring_packed_desc *d = vq->desc_packed + vq->avail_idx;
-	__virtio16 flags;
+	__virtio16 flags = cpu_to_vhost16(vq, VRING_EVENT_F_ENABLE);
 	int ret;
 
-	/* TODO: enable notification through device area */
+	if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
+		return false;
+	vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
+
+	if (vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
+		__virtio16 off_wrap = cpu_to_vhost16(vq, vq->avail_idx |
+				      vq->avail_wrap_counter << 15);
+
+		ret = vhost_update_device_off_wrap(vq, off_wrap);
+		if (ret) {
+			vq_err(vq, "Failed to write to off warp at %p: %d\n",
+			       &vq->device_event->off_wrap, ret);
+			return false;
+		}
+		/* Make sure off_wrap is wrote before flags */
+		smp_wmb();
+		flags = cpu_to_vhost16(vq, VRING_EVENT_F_DESC);
+	}
+
+	ret = vhost_update_device_flags(vq, flags);
+	if (ret) {
+		vq_err(vq, "Failed to enable notification at %p: %d\n",
+			&vq->device_event->flags, ret);
+		return false;
+	}
 
 	/* They could have slipped one in as we were doing that: make
 	 * sure it's written, then check again.
@@ -2943,7 +3095,18 @@ EXPORT_SYMBOL_GPL(vhost_enable_notify);
 static void vhost_disable_notify_packed(struct vhost_dev *dev,
 					struct vhost_virtqueue *vq)
 {
-	/* TODO: disable notification through device area */
+	__virtio16 flags;
+	int r;
+
+	if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
+		return;
+	vq->used_flags |= VRING_USED_F_NO_NOTIFY;
+
+	flags = cpu_to_vhost16(vq, VRING_EVENT_F_DISABLE);
+	r = vhost_update_device_flags(vq, flags);
+	if (r)
+		vq_err(vq, "Failed to enable notification at %p: %d\n",
+		       &vq->device_event->flags, r);
 }
 
 static void vhost_disable_notify_split(struct vhost_dev *dev,
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 73c2a78..3a7fc4b 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -96,8 +96,14 @@ struct vhost_virtqueue {
 		struct vring_desc __user *desc;
 		struct vring_packed_desc __user *desc_packed;
 	};
-	struct vring_avail __user *avail;
-	struct vring_used __user *used;
+	union {
+		struct vring_avail __user *avail;
+		struct vring_packed_desc_event __user *driver_event;
+	};
+	union {
+		struct vring_used __user *used;
+		struct vring_packed_desc_event __user *device_event;
+	};
 	const struct vhost_umem_node *meta_iotlb[VHOST_NUM_ADDRS];
 	struct file *kick;
 	struct eventfd_ctx *call_ctx;
-- 
2.7.4

[PATCH net-next V2 8/8] vhost: enable packed virtqueues

From: Jason Wang <hidden>
Date: 2018-07-16 03:29:07 

Signed-off-by: Jason Wang <redacted>
---
 drivers/vhost/vhost.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 3a7fc4b..0dfe864 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -264,7 +264,8 @@ enum {
 			 (1ULL << VIRTIO_RING_F_EVENT_IDX) |
 			 (1ULL << VHOST_F_LOG_ALL) |
 			 (1ULL << VIRTIO_F_ANY_LAYOUT) |
-			 (1ULL << VIRTIO_F_VERSION_1)
+			 (1ULL << VIRTIO_F_VERSION_1) |
+			 (1ULL << VIRTIO_F_RING_PACKED)
 };
 
 static inline bool vhost_has_feature(struct vhost_virtqueue *vq, int bit)
-- 
2.7.4

Re: [PATCH net-next V2 0/8] Packed virtqueue support for vhost

From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2018-07-16 08:39:16 

On Mon, Jul 16, 2018 at 11:28:03AM +0800, Jason Wang wrote:
Hi all:

This series implements packed virtqueues. The code were tested with
Tiwei's guest driver series at https://patchwork.ozlabs.org/cover/942297/


Pktgen test for both RX and TX does not show obvious difference with
split virtqueues. The main bottleneck is the guest Linux driver, since
it can not stress vhost for a 100% CPU utilization. A full TCP
benchmark is ongoing. Will test virtio-net pmd as well when it was
ready.
Well the question then is why we should bother merging this
if this doesn't give a performance gain. Do you see
a gain in CPU utilization maybe?

If not - let's wait for that TCP benchmark result?

Notes:
- This version depends on Tiwei's series at https://patchwork.ozlabs.org/cover/942297/

This version were tested with:

- Zerocopy (Out of Order) support
- vIOMMU support
- mergeable buffer on/off
- busy polling on/off
- vsock (nc-vsock)

Changes from V1:
- drop uapi patch and use Tiwei's
- split the enablement of packed virtqueue into a separate patch

Changes from RFC V5:

- save unnecessary barriers during vhost_add_used_packed_n()
- more compact math for event idx
- fix failure of SET_VRING_BASE when avail_wrap_counter is true
- fix not copy avail_wrap_counter during GET_VRING_BASE
- introduce SET_VRING_USED_BASE/GET_VRING_USED_BASE for syncing last_used_idx
- rename used_wrap_counter to last_used_wrap_counter
- rebase to net-next

Changes from RFC V4:

- fix signalled_used index recording
- track avail index correctly
- various minor fixes

Changes from RFC V3:

- Fix math on event idx checking
- Sync last avail wrap counter through GET/SET_VRING_BASE
- remove desc_event prefix in the driver/device structure

Changes from RFC V2:

- do not use & in checking desc_event_flags
- off should be most significant bit
- remove the workaround of mergeable buffer for dpdk prototype
- id should be in the last descriptor in the chain
- keep _F_WRITE for write descriptor when adding used
- device flags updating should use ADDR_USED type
- return error on unexpected unavail descriptor in a chain
- return false in vhost_ve_avail_empty is descriptor is available
- track last seen avail_wrap_counter
- correctly examine available descriptor in get_indirect_packed()
- vhost_idx_diff should return u16 instead of bool

Changes from RFC V1:

- Refactor vhost used elem code to avoid open coding on used elem
- Event suppression support (compile test only).
- Indirect descriptor support (compile test only).
- Zerocopy support.
- vIOMMU support.
- SCSI/VSOCK support (compile test only).
- Fix several bugs

Jason Wang (8):
  vhost: move get_rx_bufs to vhost.c
  vhost: hide used ring layout from device
  vhost: do not use vring_used_elem
  vhost_net: do not explicitly manipulate vhost_used_elem
  vhost: vhost_put_user() can accept metadata type
  vhost: packed ring support
  vhost: event suppression for packed ring
  vhost: enable packed virtqueues

 drivers/vhost/net.c        | 143 ++-----
 drivers/vhost/scsi.c       |  62 +--
 drivers/vhost/vhost.c      | 994 ++++++++++++++++++++++++++++++++++++++++-----
 drivers/vhost/vhost.h      |  55 ++-
 drivers/vhost/vsock.c      |  42 +-
 include/uapi/linux/vhost.h |   7 +
 6 files changed, 1035 insertions(+), 268 deletions(-)

-- 
2.7.4

Re: [PATCH net-next V2 0/8] Packed virtqueue support for vhost

From: Jason Wang <hidden>
Date: 2018-07-16 09:46:50 


On 2018年07月16日 16:39, Michael S. Tsirkin wrote:
On Mon, Jul 16, 2018 at 11:28:03AM +0800, Jason Wang wrote:
quoted
Hi all:

This series implements packed virtqueues. The code were tested with
Tiwei's guest driver series at https://patchwork.ozlabs.org/cover/942297/


Pktgen test for both RX and TX does not show obvious difference with
split virtqueues. The main bottleneck is the guest Linux driver, since
it can not stress vhost for a 100% CPU utilization. A full TCP
benchmark is ongoing. Will test virtio-net pmd as well when it was
ready.
Well the question then is why we should bother merging this
if this doesn't give a performance gain.
We meet bottlenecks at other places. I can only test Linux driver which 
has lots of overheads e.g interrupts. And perf show only a small 
fraction of time were spent on e.g virtqueue manipulation. I hope 
virtio-net pmd can give us different result but we don't have one ready 
for testing now. (Jen's V4 have bugs thus can not work with this series).

  Do you see
a gain in CPU utilization maybe?
Unfortunately not.

If not - let's wait for that TCP benchmark result?
We can, but you know TCP_STREAM result is sometime misleading.

A brunch of other patches of mine were rebased on this and then blocked 
on this series. Consider we don't meet regression, maybe we can merge 
this first and try optimizations or fixups on top?

Thanks

quoted
Notes:
- This version depends on Tiwei's series at https://patchwork.ozlabs.org/cover/942297/

This version were tested with:

- Zerocopy (Out of Order) support
- vIOMMU support
- mergeable buffer on/off
- busy polling on/off
- vsock (nc-vsock)

Changes from V1:
- drop uapi patch and use Tiwei's
- split the enablement of packed virtqueue into a separate patch

Changes from RFC V5:

- save unnecessary barriers during vhost_add_used_packed_n()
- more compact math for event idx
- fix failure of SET_VRING_BASE when avail_wrap_counter is true
- fix not copy avail_wrap_counter during GET_VRING_BASE
- introduce SET_VRING_USED_BASE/GET_VRING_USED_BASE for syncing last_used_idx
- rename used_wrap_counter to last_used_wrap_counter
- rebase to net-next

Changes from RFC V4:

- fix signalled_used index recording
- track avail index correctly
- various minor fixes

Changes from RFC V3:

- Fix math on event idx checking
- Sync last avail wrap counter through GET/SET_VRING_BASE
- remove desc_event prefix in the driver/device structure

Changes from RFC V2:

- do not use & in checking desc_event_flags
- off should be most significant bit
- remove the workaround of mergeable buffer for dpdk prototype
- id should be in the last descriptor in the chain
- keep _F_WRITE for write descriptor when adding used
- device flags updating should use ADDR_USED type
- return error on unexpected unavail descriptor in a chain
- return false in vhost_ve_avail_empty is descriptor is available
- track last seen avail_wrap_counter
- correctly examine available descriptor in get_indirect_packed()
- vhost_idx_diff should return u16 instead of bool

Changes from RFC V1:

- Refactor vhost used elem code to avoid open coding on used elem
- Event suppression support (compile test only).
- Indirect descriptor support (compile test only).
- Zerocopy support.
- vIOMMU support.
- SCSI/VSOCK support (compile test only).
- Fix several bugs

Jason Wang (8):
   vhost: move get_rx_bufs to vhost.c
   vhost: hide used ring layout from device
   vhost: do not use vring_used_elem
   vhost_net: do not explicitly manipulate vhost_used_elem
   vhost: vhost_put_user() can accept metadata type
   vhost: packed ring support
   vhost: event suppression for packed ring
   vhost: enable packed virtqueues

  drivers/vhost/net.c        | 143 ++-----
  drivers/vhost/scsi.c       |  62 +--
  drivers/vhost/vhost.c      | 994 ++++++++++++++++++++++++++++++++++++++++-----
  drivers/vhost/vhost.h      |  55 ++-
  drivers/vhost/vsock.c      |  42 +-
  include/uapi/linux/vhost.h |   7 +
  6 files changed, 1035 insertions(+), 268 deletions(-)

-- 
2.7.4





  

    
Re: [PATCH net-next V2 0/8] Packed virtqueue support for vhost

    

      From: "Michael S. Tsirkin" <mst@redhat.com>

      Date: 2018-07-16 12:49:16 
    

  

  
On Mon, Jul 16, 2018 at 05:46:33PM +0800, Jason Wang wrote:

On 2018年07月16日 16:39, Michael S. Tsirkin wrote:
quoted
On Mon, Jul 16, 2018 at 11:28:03AM +0800, Jason Wang wrote:
quoted
Hi all:

This series implements packed virtqueues. The code were tested with
Tiwei's guest driver series at https://patchwork.ozlabs.org/cover/942297/


Pktgen test for both RX and TX does not show obvious difference with
split virtqueues. The main bottleneck is the guest Linux driver, since
it can not stress vhost for a 100% CPU utilization. A full TCP
benchmark is ongoing. Will test virtio-net pmd as well when it was
ready.
Well the question then is why we should bother merging this
if this doesn't give a performance gain.
We meet bottlenecks at other places. I can only test Linux driver which has
lots of overheads e.g interrupts. And perf show only a small fraction of
time were spent on e.g virtqueue manipulation. I hope virtio-net pmd can
give us different result but we don't have one ready for testing now. (Jen's
V4 have bugs thus can not work with this series).
Can't linux busy poll? And how about testing loopback with XDP?

quoted
  Do you see
a gain in CPU utilization maybe?
Unfortunately not.

quoted
If not - let's wait for that TCP benchmark result?
We can, but you know TCP_STREAM result is sometime misleading.

A brunch of other patches of mine were rebased on this and then blocked on
this series. Consider we don't meet regression, maybe we can merge this
first and try optimizations or fixups on top?

Thanks
I'm not sure I understand this approach. Packed ring is just an optimization.
What value is there in merging it if it does not help speed?

quoted
quoted
Notes:
- This version depends on Tiwei's series at https://patchwork.ozlabs.org/cover/942297/

This version were tested with:

- Zerocopy (Out of Order) support
- vIOMMU support
- mergeable buffer on/off
- busy polling on/off
- vsock (nc-vsock)

Changes from V1:
- drop uapi patch and use Tiwei's
- split the enablement of packed virtqueue into a separate patch

Changes from RFC V5:

- save unnecessary barriers during vhost_add_used_packed_n()
- more compact math for event idx
- fix failure of SET_VRING_BASE when avail_wrap_counter is true
- fix not copy avail_wrap_counter during GET_VRING_BASE
- introduce SET_VRING_USED_BASE/GET_VRING_USED_BASE for syncing last_used_idx
- rename used_wrap_counter to last_used_wrap_counter
- rebase to net-next

Changes from RFC V4:

- fix signalled_used index recording
- track avail index correctly
- various minor fixes

Changes from RFC V3:

- Fix math on event idx checking
- Sync last avail wrap counter through GET/SET_VRING_BASE
- remove desc_event prefix in the driver/device structure

Changes from RFC V2:

- do not use & in checking desc_event_flags
- off should be most significant bit
- remove the workaround of mergeable buffer for dpdk prototype
- id should be in the last descriptor in the chain
- keep _F_WRITE for write descriptor when adding used
- device flags updating should use ADDR_USED type
- return error on unexpected unavail descriptor in a chain
- return false in vhost_ve_avail_empty is descriptor is available
- track last seen avail_wrap_counter
- correctly examine available descriptor in get_indirect_packed()
- vhost_idx_diff should return u16 instead of bool

Changes from RFC V1:

- Refactor vhost used elem code to avoid open coding on used elem
- Event suppression support (compile test only).
- Indirect descriptor support (compile test only).
- Zerocopy support.
- vIOMMU support.
- SCSI/VSOCK support (compile test only).
- Fix several bugs

Jason Wang (8):
   vhost: move get_rx_bufs to vhost.c
   vhost: hide used ring layout from device
   vhost: do not use vring_used_elem
   vhost_net: do not explicitly manipulate vhost_used_elem
   vhost: vhost_put_user() can accept metadata type
   vhost: packed ring support
   vhost: event suppression for packed ring
   vhost: enable packed virtqueues

  drivers/vhost/net.c        | 143 ++-----
  drivers/vhost/scsi.c       |  62 +--
  drivers/vhost/vhost.c      | 994 ++++++++++++++++++++++++++++++++++++++++-----
  drivers/vhost/vhost.h      |  55 ++-
  drivers/vhost/vsock.c      |  42 +-
  include/uapi/linux/vhost.h |   7 +
  6 files changed, 1035 insertions(+), 268 deletions(-)

-- 
2.7.4





  

    
Re: [PATCH net-next V2 0/8] Packed virtqueue support for vhost

    

      From: Jason Wang <hidden>

      Date: 2018-07-17 00:46:02 
    

  

  

On 2018年07月16日 20:49, Michael S. Tsirkin wrote:
On Mon, Jul 16, 2018 at 05:46:33PM +0800, Jason Wang wrote:
quoted
On 2018年07月16日 16:39, Michael S. Tsirkin wrote:
quoted
On Mon, Jul 16, 2018 at 11:28:03AM +0800, Jason Wang wrote:
quoted
Hi all:

This series implements packed virtqueues. The code were tested with
Tiwei's guest driver series at https://patchwork.ozlabs.org/cover/942297/


Pktgen test for both RX and TX does not show obvious difference with
split virtqueues. The main bottleneck is the guest Linux driver, since
it can not stress vhost for a 100% CPU utilization. A full TCP
benchmark is ongoing. Will test virtio-net pmd as well when it was
ready.
Well the question then is why we should bother merging this
if this doesn't give a performance gain.
We meet bottlenecks at other places. I can only test Linux driver which has
lots of overheads e.g interrupts. And perf show only a small fraction of
time were spent on e.g virtqueue manipulation. I hope virtio-net pmd can
give us different result but we don't have one ready for testing now. (Jen's
V4 have bugs thus can not work with this series).
Can't linux busy poll?
For vhost busy polling, there's no difference since guest can not give 
vhost enough stress. For guest busy polling, it does not work for the 
packets generated by pktgen.

And how about testing loopback with XDP?
No difference, I even shortcut both the tun_get_user() on host and 
netif_receive_skb() in guest.

quoted
quoted
   Do you see
a gain in CPU utilization maybe?
Unfortunately not.

quoted
If not - let's wait for that TCP benchmark result?
We can, but you know TCP_STREAM result is sometime misleading.

A brunch of other patches of mine were rebased on this and then blocked on
this series. Consider we don't meet regression, maybe we can merge this
first and try optimizations or fixups on top?

Thanks
I'm not sure I understand this approach. Packed ring is just an optimization.
What value is there in merging it if it does not help speed?
If you want to support migration from dpdk or vDPA backend. And we still 
have the chance to see the performance with virito-net pmd in the 
future. If this does not make sense for you, I will leave this series 
until we can get results from virtio-net pmd (or find a way that packed 
virtqueue outperform). And I will start to post other optimizations on 
vhost.

Thanks

quoted
quoted
quoted
Notes:
- This version depends on Tiwei's series at https://patchwork.ozlabs.org/cover/942297/

This version were tested with:

- Zerocopy (Out of Order) support
- vIOMMU support
- mergeable buffer on/off
- busy polling on/off
- vsock (nc-vsock)

Changes from V1:
- drop uapi patch and use Tiwei's
- split the enablement of packed virtqueue into a separate patch

Changes from RFC V5:

- save unnecessary barriers during vhost_add_used_packed_n()
- more compact math for event idx
- fix failure of SET_VRING_BASE when avail_wrap_counter is true
- fix not copy avail_wrap_counter during GET_VRING_BASE
- introduce SET_VRING_USED_BASE/GET_VRING_USED_BASE for syncing last_used_idx
- rename used_wrap_counter to last_used_wrap_counter
- rebase to net-next

Changes from RFC V4:

- fix signalled_used index recording
- track avail index correctly
- various minor fixes

Changes from RFC V3:

- Fix math on event idx checking
- Sync last avail wrap counter through GET/SET_VRING_BASE
- remove desc_event prefix in the driver/device structure

Changes from RFC V2:

- do not use & in checking desc_event_flags
- off should be most significant bit
- remove the workaround of mergeable buffer for dpdk prototype
- id should be in the last descriptor in the chain
- keep _F_WRITE for write descriptor when adding used
- device flags updating should use ADDR_USED type
- return error on unexpected unavail descriptor in a chain
- return false in vhost_ve_avail_empty is descriptor is available
- track last seen avail_wrap_counter
- correctly examine available descriptor in get_indirect_packed()
- vhost_idx_diff should return u16 instead of bool

Changes from RFC V1:

- Refactor vhost used elem code to avoid open coding on used elem
- Event suppression support (compile test only).
- Indirect descriptor support (compile test only).
- Zerocopy support.
- vIOMMU support.
- SCSI/VSOCK support (compile test only).
- Fix several bugs

Jason Wang (8):
    vhost: move get_rx_bufs to vhost.c
    vhost: hide used ring layout from device
    vhost: do not use vring_used_elem
    vhost_net: do not explicitly manipulate vhost_used_elem
    vhost: vhost_put_user() can accept metadata type
    vhost: packed ring support
    vhost: event suppression for packed ring
    vhost: enable packed virtqueues

   drivers/vhost/net.c        | 143 ++-----
   drivers/vhost/scsi.c       |  62 +--
   drivers/vhost/vhost.c      | 994 ++++++++++++++++++++++++++++++++++++++++-----
   drivers/vhost/vhost.h      |  55 ++-
   drivers/vhost/vsock.c      |  42 +-
   include/uapi/linux/vhost.h |   7 +
   6 files changed, 1035 insertions(+), 268 deletions(-)

-- 
2.7.4
_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization





  

    
Re: [PATCH net-next V2 0/8] Packed virtqueue support for vhost

    

      From: David Miller <davem@davemloft.net>

      Date: 2018-07-18 04:10:07 
    

  

  
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: Mon, 16 Jul 2018 15:49:04 +0300

I'm not sure I understand this approach. Packed ring is just an
optimization.  What value is there in merging it if it does not help
speed?
So it seems that both Tiwei's and Jason's packed patch sets are kind
of in limbo due to this discussion.

If I understand Jason correctly, he's trying to say that although this
work doesn't show improvements by itself, however it paves the way
such that optimizaations done in the future will be more visible.

I kind of can see Michael's viewpoint too, in that we should put this
stuff in later when it does actually show some difference.

Therefore, I'll mark both patch sets as "deferred" for now.

Let me know if I should do something else.

Thanks!





  

    
Re: [PATCH net-next V2 0/8] Packed virtqueue support for vhost

    

      From: "Michael S. Tsirkin" <mst@redhat.com>

      Date: 2018-07-22 16:56:53 
    

  

  
On Tue, Jul 17, 2018 at 08:45:16AM +0800, Jason Wang wrote:
quoted
I'm not sure I understand this approach. Packed ring is just an optimization.
What value is there in merging it if it does not help speed?
If you want to support migration from dpdk or vDPA backend.
Migration from dpdk is a mess: if you add new features you
fix migration from new one but break migration from old one.
So I'm not too worried until dpdk guys implement one of
the migration versioning proposals that have been floating
around for years.

I think vDPAs are using split ring right now. They will likely
switch to packed ring in the future, but it will probably
take some time before they do.

And we still
have the chance to see the performance with virito-net pmd in the future. If
this does not make sense for you, I will leave this series until we can get
results from virtio-net pmd (or find a way that packed virtqueue
outperform).
This makes sense to me. If there's a gain that is only
observed with the pmd driver, I think that's still fine,
but we do need to see it.

And I will start to post other optimizations on vhost.

Thanks
Thanks a lot!

-- 
MST





  

    
Re: [PATCH net-next V2 6/8] vhost: packed ring support

    

      From: Tiwei Bie <hidden>

      Date: 2018-10-12 14:34:05 
    

  

  
On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote:
[...]
quoted hunk
@@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
 		vq->last_avail_idx = s.num;
 		/* Forget the cached index value. */
 		vq->avail_idx = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			vq->last_avail_wrap_counter = wrap_counter;
+			vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+		}
 		break;
 	case VHOST_GET_VRING_BASE:
 		s.index = idx;
 		s.num = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_avail_wrap_counter << 31;
+		if (copy_to_user(argp, &s, sizeof(s)))
+			r = -EFAULT;
+		break;
+	case VHOST_SET_VRING_USED_BASE:
+		/* Moving base with an active backend?
+		 * You don't want to do that.
+		 */
+		if (vq->private_data) {
+			r = -EBUSY;
+			break;
+		}
+		if (copy_from_user(&s, argp, sizeof(s))) {
+			r = -EFAULT;
+			break;
+		}
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			wrap_counter = s.num >> 31;
+			s.num &= ~(1 << 31);
+		}
+		if (s.num > 0xffff) {
+			r = -EINVAL;
+			break;
+		}
Do we want to put wrap_counter at bit 15?

If put wrap_counter at bit 31, the check (s.num > 0xffff)
won't be able to catch the illegal index 0x8000~0xffff for
packed ring.

+		vq->last_used_idx = s.num;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			vq->last_used_wrap_counter = wrap_counter;
+		break;
+	case VHOST_GET_VRING_USED_BASE:
Do we need the new VHOST_GET_VRING_USED_BASE and
VHOST_SET_VRING_USED_BASE ops?

We are going to merge below series in DPDK:

http://patches.dpdk.org/patch/45874/

We may need to reach an agreement first.


+		s.index = idx;
+		s.num = vq->last_used_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_used_wrap_counter << 31;
 		if (copy_to_user(argp, &s, sizeof s))
 			r = -EFAULT;
 		break;
[...]





  

    
Re: [PATCH net-next V2 6/8] vhost: packed ring support

    

      From: "Michael S. Tsirkin" <mst@redhat.com>

      Date: 2018-10-12 17:23:55 
    

  

  
On Fri, Oct 12, 2018 at 10:32:44PM +0800, Tiwei Bie wrote:
On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote:
[...]
quoted
@@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
 		vq->last_avail_idx = s.num;
 		/* Forget the cached index value. */
 		vq->avail_idx = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			vq->last_avail_wrap_counter = wrap_counter;
+			vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+		}
 		break;
 	case VHOST_GET_VRING_BASE:
 		s.index = idx;
 		s.num = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_avail_wrap_counter << 31;
+		if (copy_to_user(argp, &s, sizeof(s)))
+			r = -EFAULT;
+		break;
+	case VHOST_SET_VRING_USED_BASE:
+		/* Moving base with an active backend?
+		 * You don't want to do that.
+		 */
+		if (vq->private_data) {
+			r = -EBUSY;
+			break;
+		}
+		if (copy_from_user(&s, argp, sizeof(s))) {
+			r = -EFAULT;
+			break;
+		}
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			wrap_counter = s.num >> 31;
+			s.num &= ~(1 << 31);
+		}
+		if (s.num > 0xffff) {
+			r = -EINVAL;
+			break;
+		}
Do we want to put wrap_counter at bit 15?
I think I second that - seems to be consistent with
e.g. event suppression structure and the proposed
extension to driver notifications.


If put wrap_counter at bit 31, the check (s.num > 0xffff)
won't be able to catch the illegal index 0x8000~0xffff for
packed ring.

quoted
+		vq->last_used_idx = s.num;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			vq->last_used_wrap_counter = wrap_counter;
+		break;
+	case VHOST_GET_VRING_USED_BASE:
Do we need the new VHOST_GET_VRING_USED_BASE and
VHOST_SET_VRING_USED_BASE ops?

We are going to merge below series in DPDK:

http://patches.dpdk.org/patch/45874/

We may need to reach an agreement first.


quoted
+		s.index = idx;
+		s.num = vq->last_used_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_used_wrap_counter << 31;
 		if (copy_to_user(argp, &s, sizeof s))
 			r = -EFAULT;
 		break;
[...]





  

    
Re: [PATCH net-next V2 6/8] vhost: packed ring support

    

      From: Jason Wang <hidden>

      Date: 2018-10-15 02:22:51 
    

  

  

On 2018年10月13日 01:23, Michael S. Tsirkin wrote:
On Fri, Oct 12, 2018 at 10:32:44PM +0800, Tiwei Bie wrote:
quoted
On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote:
[...]
quoted
@@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
  		vq->last_avail_idx = s.num;
  		/* Forget the cached index value. */
  		vq->avail_idx = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			vq->last_avail_wrap_counter = wrap_counter;
+			vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+		}
  		break;
  	case VHOST_GET_VRING_BASE:
  		s.index = idx;
  		s.num = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_avail_wrap_counter << 31;
+		if (copy_to_user(argp, &s, sizeof(s)))
+			r = -EFAULT;
+		break;
+	case VHOST_SET_VRING_USED_BASE:
+		/* Moving base with an active backend?
+		 * You don't want to do that.
+		 */
+		if (vq->private_data) {
+			r = -EBUSY;
+			break;
+		}
+		if (copy_from_user(&s, argp, sizeof(s))) {
+			r = -EFAULT;
+			break;
+		}
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			wrap_counter = s.num >> 31;
+			s.num &= ~(1 << 31);
+		}
+		if (s.num > 0xffff) {
+			r = -EINVAL;
+			break;
+		}
Do we want to put wrap_counter at bit 15?
I think I second that - seems to be consistent with
e.g. event suppression structure and the proposed
extension to driver notifications.
Ok, I assumes packed virtqueue support 64K but looks not. I can change 
it to bit 15 and GET_VRING_BASE need to be changed as well.

quoted
If put wrap_counter at bit 31, the check (s.num > 0xffff)
won't be able to catch the illegal index 0x8000~0xffff for
packed ring.
Do we need to clarify this in the spec?

quoted
quoted
+		vq->last_used_idx = s.num;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			vq->last_used_wrap_counter = wrap_counter;
+		break;
+	case VHOST_GET_VRING_USED_BASE:
Do we need the new VHOST_GET_VRING_USED_BASE and
VHOST_SET_VRING_USED_BASE ops?

We are going to merge below series in DPDK:

http://patches.dpdk.org/patch/45874/

We may need to reach an agreement first.
If we agree that 64K virtqueue won't be supported, I'm ok with either.

Btw the code assumes used_wrap_counter is equal to avail_wrap_counter 
which looks wrong?

Thanks

quoted
quoted
+		s.index = idx;
+		s.num = vq->last_used_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_used_wrap_counter << 31;
  		if (copy_to_user(argp, &s, sizeof s))
  			r = -EFAULT;
  		break;
[...]





  

    
Re: [PATCH net-next V2 6/8] vhost: packed ring support

    

      From: "Michael S. Tsirkin" <mst@redhat.com>

      Date: 2018-10-15 02:43:58 
    

  

  
On Mon, Oct 15, 2018 at 10:22:33AM +0800, Jason Wang wrote:

On 2018年10月13日 01:23, Michael S. Tsirkin wrote:
quoted
On Fri, Oct 12, 2018 at 10:32:44PM +0800, Tiwei Bie wrote:
quoted
On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote:
[...]
quoted
@@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
  		vq->last_avail_idx = s.num;
  		/* Forget the cached index value. */
  		vq->avail_idx = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			vq->last_avail_wrap_counter = wrap_counter;
+			vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+		}
  		break;
  	case VHOST_GET_VRING_BASE:
  		s.index = idx;
  		s.num = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_avail_wrap_counter << 31;
+		if (copy_to_user(argp, &s, sizeof(s)))
+			r = -EFAULT;
+		break;
+	case VHOST_SET_VRING_USED_BASE:
+		/* Moving base with an active backend?
+		 * You don't want to do that.
+		 */
+		if (vq->private_data) {
+			r = -EBUSY;
+			break;
+		}
+		if (copy_from_user(&s, argp, sizeof(s))) {
+			r = -EFAULT;
+			break;
+		}
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			wrap_counter = s.num >> 31;
+			s.num &= ~(1 << 31);
+		}
+		if (s.num > 0xffff) {
+			r = -EINVAL;
+			break;
+		}
Do we want to put wrap_counter at bit 15?
I think I second that - seems to be consistent with
e.g. event suppression structure and the proposed
extension to driver notifications.
Ok, I assumes packed virtqueue support 64K but looks not. I can change it to
bit 15 and GET_VRING_BASE need to be changed as well.

quoted
quoted
If put wrap_counter at bit 31, the check (s.num > 0xffff)
won't be able to catch the illegal index 0x8000~0xffff for
packed ring.
Do we need to clarify this in the spec?
Isn't this all internal vhost stuff?

quoted
quoted
quoted
+		vq->last_used_idx = s.num;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			vq->last_used_wrap_counter = wrap_counter;
+		break;
+	case VHOST_GET_VRING_USED_BASE:
Do we need the new VHOST_GET_VRING_USED_BASE and
VHOST_SET_VRING_USED_BASE ops?

We are going to merge below series in DPDK:

http://patches.dpdk.org/patch/45874/

We may need to reach an agreement first.
If we agree that 64K virtqueue won't be supported, I'm ok with either.
Well the spec says right at the beginning:

Packed virtqueues support up to 2 15 entries each.


Btw the code assumes used_wrap_counter is equal to avail_wrap_counter which
looks wrong?

Thanks

quoted
quoted
quoted
+		s.index = idx;
+		s.num = vq->last_used_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_used_wrap_counter << 31;
  		if (copy_to_user(argp, &s, sizeof s))
  			r = -EFAULT;
  		break;
[...]





  

    
Re: [PATCH net-next V2 6/8] vhost: packed ring support

    

      From: Jason Wang <hidden>

      Date: 2018-10-15 02:51:23 
    

  

  

On 2018年10月15日 10:43, Michael S. Tsirkin wrote:
On Mon, Oct 15, 2018 at 10:22:33AM +0800, Jason Wang wrote:
quoted
On 2018年10月13日 01:23, Michael S. Tsirkin wrote:
quoted
On Fri, Oct 12, 2018 at 10:32:44PM +0800, Tiwei Bie wrote:
quoted
On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote:
[...]
quoted
@@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
   		vq->last_avail_idx = s.num;
   		/* Forget the cached index value. */
   		vq->avail_idx = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			vq->last_avail_wrap_counter = wrap_counter;
+			vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+		}
   		break;
   	case VHOST_GET_VRING_BASE:
   		s.index = idx;
   		s.num = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_avail_wrap_counter << 31;
+		if (copy_to_user(argp, &s, sizeof(s)))
+			r = -EFAULT;
+		break;
+	case VHOST_SET_VRING_USED_BASE:
+		/* Moving base with an active backend?
+		 * You don't want to do that.
+		 */
+		if (vq->private_data) {
+			r = -EBUSY;
+			break;
+		}
+		if (copy_from_user(&s, argp, sizeof(s))) {
+			r = -EFAULT;
+			break;
+		}
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			wrap_counter = s.num >> 31;
+			s.num &= ~(1 << 31);
+		}
+		if (s.num > 0xffff) {
+			r = -EINVAL;
+			break;
+		}
Do we want to put wrap_counter at bit 15?
I think I second that - seems to be consistent with
e.g. event suppression structure and the proposed
extension to driver notifications.
Ok, I assumes packed virtqueue support 64K but looks not. I can change it to
bit 15 and GET_VRING_BASE need to be changed as well.

quoted
quoted
If put wrap_counter at bit 31, the check (s.num > 0xffff)
won't be able to catch the illegal index 0x8000~0xffff for
packed ring.
Do we need to clarify this in the spec?
Isn't this all internal vhost stuff?
I meant the illegal index 0x8000-0xffff.

quoted
quoted
quoted
quoted
+		vq->last_used_idx = s.num;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			vq->last_used_wrap_counter = wrap_counter;
+		break;
+	case VHOST_GET_VRING_USED_BASE:
Do we need the new VHOST_GET_VRING_USED_BASE and
VHOST_SET_VRING_USED_BASE ops?

We are going to merge below series in DPDK:

http://patches.dpdk.org/patch/45874/

We may need to reach an agreement first.
If we agree that 64K virtqueue won't be supported, I'm ok with either.
Well the spec says right at the beginning:

Packed virtqueues support up to 2 15 entries each.
Ok. I get it.

Then I can change vhost to match what dpdk did.

Thanks

quoted
Btw the code assumes used_wrap_counter is equal to avail_wrap_counter which
looks wrong?

Thanks

quoted
quoted
quoted
+		s.index = idx;
+		s.num = vq->last_used_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_used_wrap_counter << 31;
   		if (copy_to_user(argp, &s, sizeof s))
   			r = -EFAULT;
   		break;
[...]





  

    
Re: [PATCH net-next V2 6/8] vhost: packed ring support

    

      From: "Michael S. Tsirkin" <mst@redhat.com>

      Date: 2018-10-15 10:25:18 
    

  

  
On Mon, Oct 15, 2018 at 10:51:06AM +0800, Jason Wang wrote:

On 2018年10月15日 10:43, Michael S. Tsirkin wrote:
quoted
On Mon, Oct 15, 2018 at 10:22:33AM +0800, Jason Wang wrote:
quoted
On 2018年10月13日 01:23, Michael S. Tsirkin wrote:
quoted
On Fri, Oct 12, 2018 at 10:32:44PM +0800, Tiwei Bie wrote:
quoted
On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote:
[...]
quoted
@@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
   		vq->last_avail_idx = s.num;
   		/* Forget the cached index value. */
   		vq->avail_idx = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			vq->last_avail_wrap_counter = wrap_counter;
+			vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+		}
   		break;
   	case VHOST_GET_VRING_BASE:
   		s.index = idx;
   		s.num = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_avail_wrap_counter << 31;
+		if (copy_to_user(argp, &s, sizeof(s)))
+			r = -EFAULT;
+		break;
+	case VHOST_SET_VRING_USED_BASE:
+		/* Moving base with an active backend?
+		 * You don't want to do that.
+		 */
+		if (vq->private_data) {
+			r = -EBUSY;
+			break;
+		}
+		if (copy_from_user(&s, argp, sizeof(s))) {
+			r = -EFAULT;
+			break;
+		}
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			wrap_counter = s.num >> 31;
+			s.num &= ~(1 << 31);
+		}
+		if (s.num > 0xffff) {
+			r = -EINVAL;
+			break;
+		}
Do we want to put wrap_counter at bit 15?
I think I second that - seems to be consistent with
e.g. event suppression structure and the proposed
extension to driver notifications.
Ok, I assumes packed virtqueue support 64K but looks not. I can change it to
bit 15 and GET_VRING_BASE need to be changed as well.

quoted
quoted
If put wrap_counter at bit 31, the check (s.num > 0xffff)
won't be able to catch the illegal index 0x8000~0xffff for
packed ring.
Do we need to clarify this in the spec?
Isn't this all internal vhost stuff?
I meant the illegal index 0x8000-0xffff.
It does say packed virtqueues support up to 2 15 entries each.

But yes we can add a requirement that devices do not expose
larger rings. Split does not support 2**16 either, right?
With 2**16 enties avail index becomes 0 and ring looks empty.

quoted
quoted
quoted
quoted
quoted
+		vq->last_used_idx = s.num;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			vq->last_used_wrap_counter = wrap_counter;
+		break;
+	case VHOST_GET_VRING_USED_BASE:
Do we need the new VHOST_GET_VRING_USED_BASE and
VHOST_SET_VRING_USED_BASE ops?

We are going to merge below series in DPDK:

http://patches.dpdk.org/patch/45874/

We may need to reach an agreement first.
If we agree that 64K virtqueue won't be supported, I'm ok with either.
Well the spec says right at the beginning:

Packed virtqueues support up to 2 15 entries each.
Ok. I get it.

Then I can change vhost to match what dpdk did.

Thanks

quoted
quoted
Btw the code assumes used_wrap_counter is equal to avail_wrap_counter which
looks wrong?

Thanks

quoted
quoted
quoted
+		s.index = idx;
+		s.num = vq->last_used_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_used_wrap_counter << 31;
   		if (copy_to_user(argp, &s, sizeof s))
   			r = -EFAULT;
   		break;
[...]





  

    
Re: [PATCH net-next V2 6/8] vhost: packed ring support

    

      From: Maxime Coquelin <hidden>

      Date: 2018-10-16 13:58:37 
    

  

  
On 10/15/2018 04:22 AM, Jason Wang wrote:

On 2018年10月13日 01:23, Michael S. Tsirkin wrote:
quoted
On Fri, Oct 12, 2018 at 10:32:44PM +0800, Tiwei Bie wrote:
quoted
On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote:
[...]
quoted
@@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev *d, 
unsigned int ioctl, void __user *arg
          vq->last_avail_idx = s.num;
          /* Forget the cached index value. */
          vq->avail_idx = vq->last_avail_idx;
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+            vq->last_avail_wrap_counter = wrap_counter;
+            vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+        }
          break;
      case VHOST_GET_VRING_BASE:
          s.index = idx;
          s.num = vq->last_avail_idx;
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+            s.num |= vq->last_avail_wrap_counter << 31;
+        if (copy_to_user(argp, &s, sizeof(s)))
+            r = -EFAULT;
+        break;
+    case VHOST_SET_VRING_USED_BASE:
+        /* Moving base with an active backend?
+         * You don't want to do that.
+         */
+        if (vq->private_data) {
+            r = -EBUSY;
+            break;
+        }
+        if (copy_from_user(&s, argp, sizeof(s))) {
+            r = -EFAULT;
+            break;
+        }
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+            wrap_counter = s.num >> 31;
+            s.num &= ~(1 << 31);
+        }
+        if (s.num > 0xffff) {
+            r = -EINVAL;
+            break;
+        }
Do we want to put wrap_counter at bit 15?
I think I second that - seems to be consistent with
e.g. event suppression structure and the proposed
extension to driver notifications.
Ok, I assumes packed virtqueue support 64K but looks not. I can change 
it to bit 15 and GET_VRING_BASE need to be changed as well.

quoted
quoted
If put wrap_counter at bit 31, the check (s.num > 0xffff)
won't be able to catch the illegal index 0x8000~0xffff for
packed ring.
Do we need to clarify this in the spec?

quoted
quoted
quoted
+        vq->last_used_idx = s.num;
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+            vq->last_used_wrap_counter = wrap_counter;
+        break;
+    case VHOST_GET_VRING_USED_BASE:
Do we need the new VHOST_GET_VRING_USED_BASE and
VHOST_SET_VRING_USED_BASE ops?

We are going to merge below series in DPDK:

http://patches.dpdk.org/patch/45874/

We may need to reach an agreement first.
If we agree that 64K virtqueue won't be supported, I'm ok with either.
I'm fine to put wrap_counter at bit 15.
I will post a new version of the DPDK series soon.

Btw the code assumes used_wrap_counter is equal to avail_wrap_counter 
which looks wrong?
For split ring, we used to set the last_used_idx to the same value as
last_avail_idx as VHOST_USER_GET_VRING_BASE cannot be called while the
ring is being processed, so their value is always the same at the time
the request is handled.

I kept the same behavior for packed ring, and so the wrap counter have
to be the same.

Regards,
Maxime

Thanks

quoted
quoted
quoted
+        s.index = idx;
+        s.num = vq->last_used_idx;
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+            s.num |= vq->last_used_wrap_counter << 31;
          if (copy_to_user(argp, &s, sizeof s))
              r = -EFAULT;
          break;
[...]





  

    
Re: [PATCH net-next V2 6/8] vhost: packed ring support

    

      From: Jason Wang <hidden>

      Date: 2018-10-17 06:54:39 
    

  

  
On 2018/10/16 下午9:58, Maxime Coquelin wrote:
On 10/15/2018 04:22 AM, Jason Wang wrote:
quoted

On 2018年10月13日 01:23, Michael S. Tsirkin wrote:
quoted
On Fri, Oct 12, 2018 at 10:32:44PM +0800, Tiwei Bie wrote:
quoted
On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote:
[...]
quoted
@@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev 
*d, unsigned int ioctl, void __user *arg
          vq->last_avail_idx = s.num;
          /* Forget the cached index value. */
          vq->avail_idx = vq->last_avail_idx;
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+            vq->last_avail_wrap_counter = wrap_counter;
+            vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+        }
          break;
      case VHOST_GET_VRING_BASE:
          s.index = idx;
          s.num = vq->last_avail_idx;
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+            s.num |= vq->last_avail_wrap_counter << 31;
+        if (copy_to_user(argp, &s, sizeof(s)))
+            r = -EFAULT;
+        break;
+    case VHOST_SET_VRING_USED_BASE:
+        /* Moving base with an active backend?
+         * You don't want to do that.
+         */
+        if (vq->private_data) {
+            r = -EBUSY;
+            break;
+        }
+        if (copy_from_user(&s, argp, sizeof(s))) {
+            r = -EFAULT;
+            break;
+        }
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+            wrap_counter = s.num >> 31;
+            s.num &= ~(1 << 31);
+        }
+        if (s.num > 0xffff) {
+            r = -EINVAL;
+            break;
+        }
Do we want to put wrap_counter at bit 15?
I think I second that - seems to be consistent with
e.g. event suppression structure and the proposed
extension to driver notifications.
Ok, I assumes packed virtqueue support 64K but looks not. I can 
change it to bit 15 and GET_VRING_BASE need to be changed as well.

quoted
quoted
If put wrap_counter at bit 31, the check (s.num > 0xffff)
won't be able to catch the illegal index 0x8000~0xffff for
packed ring.
Do we need to clarify this in the spec?

quoted
quoted
quoted
+        vq->last_used_idx = s.num;
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+            vq->last_used_wrap_counter = wrap_counter;
+        break;
+    case VHOST_GET_VRING_USED_BASE:
Do we need the new VHOST_GET_VRING_USED_BASE and
VHOST_SET_VRING_USED_BASE ops?

We are going to merge below series in DPDK:

http://patches.dpdk.org/patch/45874/

We may need to reach an agreement first.
If we agree that 64K virtqueue won't be supported, I'm ok with either.
I'm fine to put wrap_counter at bit 15.
I will post a new version of the DPDK series soon.

quoted
Btw the code assumes used_wrap_counter is equal to avail_wrap_counter 
which looks wrong?
For split ring, we used to set the last_used_idx to the same value as
last_avail_idx as VHOST_USER_GET_VRING_BASE cannot be called while the
ring is being processed, so their value is always the same at the time
the request is handled.

I may miss something, but it looks to me we should sync last_used_idx 
from used_idx.

Thanks



I kept the same behavior for packed ring, and so the wrap counter have
to be the same.

Regards,
Maxime

quoted
Thanks

quoted
quoted
quoted
+        s.index = idx;
+        s.num = vq->last_used_idx;
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+            s.num |= vq->last_used_wrap_counter << 31;
          if (copy_to_user(argp, &s, sizeof s))
              r = -EFAULT;
          break;
[...]





  

    
Re: [PATCH net-next V2 6/8] vhost: packed ring support

    

      From: Maxime Coquelin <hidden>

      Date: 2018-10-17 12:02:55 
    

  

  

On 10/17/2018 08:54 AM, Jason Wang wrote:
On 2018/10/16 下午9:58, Maxime Coquelin wrote:
quoted
On 10/15/2018 04:22 AM, Jason Wang wrote:
quoted

On 2018年10月13日 01:23, Michael S. Tsirkin wrote:
quoted
On Fri, Oct 12, 2018 at 10:32:44PM +0800, Tiwei Bie wrote:
quoted
On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote:
[...]
quoted
@@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev 
*d, unsigned int ioctl, void __user *arg
          vq->last_avail_idx = s.num;
          /* Forget the cached index value. */
          vq->avail_idx = vq->last_avail_idx;
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+            vq->last_avail_wrap_counter = wrap_counter;
+            vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+        }
          break;
      case VHOST_GET_VRING_BASE:
          s.index = idx;
          s.num = vq->last_avail_idx;
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+            s.num |= vq->last_avail_wrap_counter << 31;
+        if (copy_to_user(argp, &s, sizeof(s)))
+            r = -EFAULT;
+        break;
+    case VHOST_SET_VRING_USED_BASE:
+        /* Moving base with an active backend?
+         * You don't want to do that.
+         */
+        if (vq->private_data) {
+            r = -EBUSY;
+            break;
+        }
+        if (copy_from_user(&s, argp, sizeof(s))) {
+            r = -EFAULT;
+            break;
+        }
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+            wrap_counter = s.num >> 31;
+            s.num &= ~(1 << 31);
+        }
+        if (s.num > 0xffff) {
+            r = -EINVAL;
+            break;
+        }
Do we want to put wrap_counter at bit 15?
I think I second that - seems to be consistent with
e.g. event suppression structure and the proposed
extension to driver notifications.
Ok, I assumes packed virtqueue support 64K but looks not. I can 
change it to bit 15 and GET_VRING_BASE need to be changed as well.

quoted
quoted
If put wrap_counter at bit 31, the check (s.num > 0xffff)
won't be able to catch the illegal index 0x8000~0xffff for
packed ring.
Do we need to clarify this in the spec?

quoted
quoted
quoted
+        vq->last_used_idx = s.num;
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+            vq->last_used_wrap_counter = wrap_counter;
+        break;
+    case VHOST_GET_VRING_USED_BASE:
Do we need the new VHOST_GET_VRING_USED_BASE and
VHOST_SET_VRING_USED_BASE ops?

We are going to merge below series in DPDK:

http://patches.dpdk.org/patch/45874/

We may need to reach an agreement first.
If we agree that 64K virtqueue won't be supported, I'm ok with either.
I'm fine to put wrap_counter at bit 15.
I will post a new version of the DPDK series soon.

quoted
Btw the code assumes used_wrap_counter is equal to avail_wrap_counter 
which looks wrong?
For split ring, we used to set the last_used_idx to the same value as
last_avail_idx as VHOST_USER_GET_VRING_BASE cannot be called while the
ring is being processed, so their value is always the same at the time
the request is handled.

I may miss something, but it looks to me we should sync last_used_idx 
from used_idx.
Ok, so as proposed off-list by Jason, we could extend
VHOST_USER_[GET|SET]_VRING_BASE to have the following payload when
VIRTIO_F_RING_PACKED is negotiated:

Bit[0:14] avail index
Bit[15] avail wrap counter
Bit[16:30] used index
Bit[31] used wrap counter

Is everyone ok with that?

Another thing that I'd like to discuss is how do we reconnect in case of
user backend crash. When it happens, the frontend hasn't queried the
backend for last_avail_idx/last_used_idx and their wrap counters.

With split ring, when it happens, we set last_avail_idx to device's used
index (see virtio_queue_restore_last_avail_idx()).
Problem with packed ring is that wrap counters information is only in 
the backend.

Can we get device's used index and deduce the wrap counter value from
corresponding descriptor flag?

Any thoughts?

Regards,
Maxime
Thanks


quoted

I kept the same behavior for packed ring, and so the wrap counter have
to be the same.

Regards,
Maxime

quoted
Thanks

quoted
quoted
quoted
+        s.index = idx;
+        s.num = vq->last_used_idx;
+        if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+            s.num |= vq->last_used_wrap_counter << 31;
          if (copy_to_user(argp, &s, sizeof s))
              r = -EFAULT;
          break;
[...]





  

    
Re: [PATCH net-next V2 6/8] vhost: packed ring support

    

      From: Jason Wang <hidden>

      Date: 2018-10-18 02:44:53 
    

  

  
On 2018/10/15 下午6:25, Michael S. Tsirkin wrote:
On Mon, Oct 15, 2018 at 10:51:06AM +0800, Jason Wang wrote:
quoted
On 2018年10月15日 10:43, Michael S. Tsirkin wrote:
quoted
On Mon, Oct 15, 2018 at 10:22:33AM +0800, Jason Wang wrote:
quoted
On 2018年10月13日 01:23, Michael S. Tsirkin wrote:
quoted
On Fri, Oct 12, 2018 at 10:32:44PM +0800, Tiwei Bie wrote:
quoted
On Mon, Jul 16, 2018 at 11:28:09AM +0800, Jason Wang wrote:
[...]
quoted
@@ -1367,10 +1397,48 @@ long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *arg
    		vq->last_avail_idx = s.num;
    		/* Forget the cached index value. */
    		vq->avail_idx = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			vq->last_avail_wrap_counter = wrap_counter;
+			vq->avail_wrap_counter = vq->last_avail_wrap_counter;
+		}
    		break;
    	case VHOST_GET_VRING_BASE:
    		s.index = idx;
    		s.num = vq->last_avail_idx;
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED))
+			s.num |= vq->last_avail_wrap_counter << 31;
+		if (copy_to_user(argp, &s, sizeof(s)))
+			r = -EFAULT;
+		break;
+	case VHOST_SET_VRING_USED_BASE:
+		/* Moving base with an active backend?
+		 * You don't want to do that.
+		 */
+		if (vq->private_data) {
+			r = -EBUSY;
+			break;
+		}
+		if (copy_from_user(&s, argp, sizeof(s))) {
+			r = -EFAULT;
+			break;
+		}
+		if (vhost_has_feature(vq, VIRTIO_F_RING_PACKED)) {
+			wrap_counter = s.num >> 31;
+			s.num &= ~(1 << 31);
+		}
+		if (s.num > 0xffff) {
+			r = -EINVAL;
+			break;
+		}
Do we want to put wrap_counter at bit 15?
I think I second that - seems to be consistent with
e.g. event suppression structure and the proposed
extension to driver notifications.
Ok, I assumes packed virtqueue support 64K but looks not. I can change it to
bit 15 and GET_VRING_BASE need to be changed as well.

quoted
quoted
If put wrap_counter at bit 31, the check (s.num > 0xffff)
won't be able to catch the illegal index 0x8000~0xffff for
packed ring.
Do we need to clarify this in the spec?
Isn't this all internal vhost stuff?
I meant the illegal index 0x8000-0xffff.
It does say packed virtqueues support up to 2 15 entries each.

But yes we can add a requirement that devices do not expose
larger rings. Split does not support 2**16 either, right?
With 2**16 enties avail index becomes 0 and ring looks empty.
Yes, so it's better to clarify this in the spec.

Thanks


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