Re: [PATCH 2/4] vhost: introduce vhost_log_write
From: Victor Kaplansky <hidden>
Date: 2015-12-02 13:53:05
On Wed, Dec 02, 2015 at 11:43:11AM +0800, Yuanhan Liu wrote:
quoted hunk ↗ jump to hunk
Introduce vhost_log_write() helper function to log the dirty pages we touched. Page size is harded code to 4096 (VHOST_LOG_PAGE), and each log is presented by 1 bit. Therefore, vhost_log_write() simply finds the right bit for related page we are gonna change, and set it to 1. dev->log_base denotes the start of the dirty page bitmap. The page address is biased by log_guest_addr, which is derived from SET_VRING_ADDR request as part of the vring related addresses. Signed-off-by: Yuanhan Liu <redacted> --- lib/librte_vhost/rte_virtio_net.h | 34 ++++++++++++++++++++++++++++++++++ lib/librte_vhost/virtio-net.c | 4 ++++ 2 files changed, 38 insertions(+)diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h index 416dac2..191c1be 100644 --- a/lib/librte_vhost/rte_virtio_net.h +++ b/lib/librte_vhost/rte_virtio_net.h@@ -40,6 +40,7 @@ */ #include <stdint.h> +#include <linux/vhost.h> #include <linux/virtio_ring.h> #include <linux/virtio_net.h> #include <sys/eventfd.h>@@ -59,6 +60,8 @@ struct rte_mbuf; /* Backend value set by guest. */ #define VIRTIO_DEV_STOPPED -1 +#define VHOST_LOG_PAGE 4096 + /* Enum for virtqueue management. */ enum {VIRTIO_RXQ, VIRTIO_TXQ, VIRTIO_QNUM};@@ -82,6 +85,7 @@ struct vhost_virtqueue { struct vring_desc *desc; /**< Virtqueue descriptor ring. */ struct vring_avail *avail; /**< Virtqueue available ring. */ struct vring_used *used; /**< Virtqueue used ring. */ + uint64_t log_guest_addr; /**< Physical address of used ring, for logging */ uint32_t size; /**< Size of descriptor ring. */ uint32_t backend; /**< Backend value to determine if device should started/stopped. */ uint16_t vhost_hlen; /**< Vhost header length (varies depending on RX merge buffers. */@@ -203,6 +207,36 @@ gpa_to_vva(struct virtio_net *dev, uint64_t guest_pa) return vhost_va; } +static inline void __attribute__((always_inline)) +vhost_log_page(uint8_t *log_base, uint64_t page) +{ + /* TODO: to make it atomic? */ + log_base[page / 8] |= 1 << (page % 8);
I think the atomic OR operation is necessary only if there can be more than one vhost-user back-end updating the guest's memory simultaneously. However probably it is pretty safe to perform regular OR operation, since rings are not shared between back-end. What about buffers pointed by descriptors? To be on the safe side, I would use a GCC built-in function __sync_fetch_and_or().
+}
+
+static inline void __attribute__((always_inline))
+vhost_log_write(struct virtio_net *dev, struct vhost_virtqueue *vq,
+ uint64_t offset, uint64_t len)
+{
+ uint64_t addr = vq->log_guest_addr;
+ uint64_t page;
+
+ if (unlikely(((dev->features & (1ULL << VHOST_F_LOG_ALL)) == 0) ||
+ !dev->log_base || !len))
+ return;Isn't "likely" more appropriate in above, since the whole expression is expected to be true most of the time?
quoted hunk ↗ jump to hunk
+ + addr += offset; + if (dev->log_size < ((addr + len - 1) / VHOST_LOG_PAGE / 8)) + return; + + page = addr / VHOST_LOG_PAGE; + while (page * VHOST_LOG_PAGE < addr + len) { + vhost_log_page(dev->log_base, page); + page += VHOST_LOG_PAGE; + } +} + + /** * Disable features in feature_mask. Returns 0 on success. */diff --git a/lib/librte_vhost/virtio-net.c b/lib/librte_vhost/virtio-net.c index 8364938..4481827 100644 --- a/lib/librte_vhost/virtio-net.c +++ b/lib/librte_vhost/virtio-net.c@@ -666,12 +666,16 @@ set_vring_addr(struct vhost_device_ctx ctx, struct vhost_vring_addr *addr) return -1; } + vq->log_guest_addr = addr->log_guest_addr; + LOG_DEBUG(VHOST_CONFIG, "(%"PRIu64") mapped address desc: %p\n", dev->device_fh, vq->desc); LOG_DEBUG(VHOST_CONFIG, "(%"PRIu64") mapped address avail: %p\n", dev->device_fh, vq->avail); LOG_DEBUG(VHOST_CONFIG, "(%"PRIu64") mapped address used: %p\n", dev->device_fh, vq->used); + LOG_DEBUG(VHOST_CONFIG, "(%"PRIu64") log_guest_addr: %p\n", + dev->device_fh, (void *)(uintptr_t)vq->log_guest_addr); return 0; }-- 1.9.0