Re: [PATCH 3/5] VSOCK: support receive mergeable rx buffer in guest

On 2018/11/7 下午3:07, jiangyiwen wrote:

On 2018/11/7 14:20, Jason Wang wrote:

quoted

On 2018/11/6 下午2:41, jiangyiwen wrote:

quoted

On 2018/11/6 12:00, Jason Wang wrote:

quoted

On 2018/11/5 下午3:47, jiangyiwen wrote:

quoted

Guest receive mergeable rx buffer, it can merge
scatter rx buffer into a big buffer and then copy
to user space.

Signed-off-by: Yiwen Jiang<redacted>
---
    include/linux/virtio_vsock.h            |  9 ++++
    net/vmw_vsock/virtio_transport.c        | 75 +++++++++++++++++++++++++++++----
    net/vmw_vsock/virtio_transport_common.c | 59 ++++++++++++++++++++++----
    3 files changed, 127 insertions(+), 16 deletions(-)

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index da9e1fe..6be3cd7 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h

@@ -13,6 +13,8 @@
    #define VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE    (1024 * 4)
    #define VIRTIO_VSOCK_MAX_BUF_SIZE        0xFFFFFFFFUL
    #define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE        (1024 * 64)
+/* virtio_vsock_pkt + max_pkt_len(default MAX_PKT_BUF_SIZE) */
+#define VIRTIO_VSOCK_MAX_MRG_BUF_NUM ((VIRTIO_VSOCK_MAX_PKT_BUF_SIZE / PAGE_SIZE) + 1)

    /* Virtio-vsock feature */
    #define VIRTIO_VSOCK_F_MRG_RXBUF 0 /* Host can merge receive buffers. */

@@ -48,6 +50,11 @@ struct virtio_vsock_sock {
        struct list_head rx_queue;
    };

+struct virtio_vsock_mrg_rxbuf {
+    void *buf;
+    u32 len;
+};
+
    struct virtio_vsock_pkt {
        struct virtio_vsock_hdr    hdr;
        struct virtio_vsock_mrg_rxbuf_hdr mrg_rxbuf_hdr;

@@ -59,6 +66,8 @@ struct virtio_vsock_pkt {
        u32 len;
        u32 off;
        bool reply;
+    bool mergeable;
+    struct virtio_vsock_mrg_rxbuf mrg_rxbuf[VIRTIO_VSOCK_MAX_MRG_BUF_NUM];
    };

It's better to use iov here I think, and drop buf completely.

And this is better to be done in an independent patch.

You're right, I can use kvec instead of customized structure,
in addition, I don't understand about drop buf completely and
an independent patch.

I mean there a void *buf in struct virtio_vsock_pkt. You can drop it and switch to use iov(iter) or other data structure that supports sg.

Thanks

Yes, I understand your idea, I don't want to modify tx process method, so I
keep the buf.

I'm afraid this will end of codes that is hard to be maintained. Let's 
try to unify them.

Thanks

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