[PATCH v2] Update event idx if guest has made extra buffers during double check

[PATCH v2] Update event idx if guest has made extra buffers during double check

[thomas]

If guest has made some buffers available during double check,
but the total buffer size available is lower than @bufsize,
notify the guest with the latest available idx(event idx)
seen by the host.

Fixes: 06b12970174 ("virtio-net: fix network stall under load")
Signed-off-by: wencheng Yang <east.moutain.yang@gmail.com>
---
 hw/net/virtio-net.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 9c7e85caea..23c6c8c898 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1654,6 +1654,7 @@ static int virtio_net_has_buffers(VirtIONetQueue *q, int bufsize)
         if (virtio_queue_empty(q->rx_vq) ||
             (n->mergeable_rx_bufs &&
              !virtqueue_avail_bytes(q->rx_vq, bufsize, 0))) {
+            virtio_queue_set_notification(q->rx_vq, 1);
             return 0;
         }
     }
-- 
2.39.0

Re: [PATCH v2] Update event idx if guest has made extra buffers during double check

[Michael Tokarev]

17.06.2024 08:45, thomas wrote:
> If guest has made some buffers available during double check,
> but the total buffer size available is lower than @bufsize,
> notify the guest with the latest available idx(event idx)
> seen by the host.

Hi!

Has this change been forgotten, or is it not needed anymore?

Thanks,

/mjt

> Fixes: 06b12970174 ("virtio-net: fix network stall under load")
> Signed-off-by: wencheng Yang <east.moutain.yang@gmail.com>
> ---
>   hw/net/virtio-net.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 9c7e85caea..23c6c8c898 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -1654,6 +1654,7 @@ static int virtio_net_has_buffers(VirtIONetQueue *q, int bufsize)
>           if (virtio_queue_empty(q->rx_vq) ||
>               (n->mergeable_rx_bufs &&
>                !virtqueue_avail_bytes(q->rx_vq, bufsize, 0))) {
> +            virtio_queue_set_notification(q->rx_vq, 1);
>               return 0;
>           }
>       }

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Re: [PATCH v2] Update event idx if guest has made extra buffers during double check

[Michael S. Tsirkin]

On Mon, Jun 17, 2024 at 01:45:51PM +0800, thomas wrote:
> If guest has made some buffers available during double check,
> but the total buffer size available is lower than @bufsize,
> notify the guest with the latest available idx(event idx)
> seen by the host.
> 
> Fixes: 06b12970174 ("virtio-net: fix network stall under load")
> Signed-off-by: wencheng Yang <east.moutain.yang@gmail.com>
> ---
>  hw/net/virtio-net.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 9c7e85caea..23c6c8c898 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -1654,6 +1654,7 @@ static int virtio_net_has_buffers(VirtIONetQueue *q, int bufsize)
>          if (virtio_queue_empty(q->rx_vq) ||
>              (n->mergeable_rx_bufs &&
>               !virtqueue_avail_bytes(q->rx_vq, bufsize, 0))) {
> +            virtio_queue_set_notification(q->rx_vq, 1);


This raises a lot of questions, but first of all virtio_queue_set_notification
does not notify guest, it enables guest notifications.

>              return 0;
>          }
>      }
> -- 
> 2.39.0