Re: [PATCH 19.11] net/virtio-user: fix socket non-blocking mode

[Christian Ehrhardt <christian.ehrhardt@canonical.com>]

On Thu, Jul 14, 2022 at 11:22 AM Yuan Wang <yuanx.wang@intel.com> wrote:
>
> [ upstream commit 41f9a1757ffc010cc3debaad9a56af8ad88d0c6d ]

Thank you,
your patch was in time, but sadly a few fell through the cracks on my side.
(and many more just arrived too late).

Your patch is applied to the WIP branch now, but currently testing of
-rc1 is going on which I do not want to disrupt.

If we need an -rc2 anyway or generally have the time to do an -rc2
without too much disruption it will be in 19.11.13, otherwise it is
already queued for 19.11.14


> The virtio-user initialization requires unix socket to receive backend
> messages in block mode. However, virtio_user_read_dev_config() sets
> the same socket to nonblocking via fcntl, which affects all threads.
> Enabling the rxq interrupt can causes both of these behaviors to occur
> concurrently, with the result that the initialization may fail
> because no messages are received in nonblocking socket.
>
> Fix that by replacing O_NONBLOCK with the recv per-call option
> MSG_DONTWAIT.
>
> Fixes: ef53b6030039 ("net/virtio-user: support LSC")
>
> Signed-off-by: Yuan Wang <yuanx.wang@intel.com>
> Acked-by: Stephen Hemminger <stephen@networkplumber.org>
> Reviewed-by: Chenbo Xia <chenbo.xia@intel.com>
> ---
>  drivers/net/virtio/virtio_user_ethdev.c | 15 ++-------------
>  1 file changed, 2 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/net/virtio/virtio_user_ethdev.c b/drivers/net/virtio/virtio_user_ethdev.c
> index 2fccf9fce..1c07caeb5 100644
> --- a/drivers/net/virtio/virtio_user_ethdev.c
> +++ b/drivers/net/virtio/virtio_user_ethdev.c
> @@ -211,15 +211,9 @@ virtio_user_read_dev_config(struct virtio_hw *hw, size_t offset,
>
>                 if (dev->vhostfd >= 0) {
>                         int r;
> -                       int flags;
>
> -                       flags = fcntl(dev->vhostfd, F_GETFL);
> -                       if (fcntl(dev->vhostfd, F_SETFL,
> -                                       flags | O_NONBLOCK) == -1) {
> -                               PMD_DRV_LOG(ERR, "error setting O_NONBLOCK flag");
> -                               return;
> -                       }
> -                       r = recv(dev->vhostfd, buf, 128, MSG_PEEK);
> +                       r = recv(dev->vhostfd, buf, 128,
> +                                      MSG_PEEK | MSG_DONTWAIT);
>                         if (r == 0 || (r < 0 && errno != EAGAIN)) {
>                                 dev->net_status &= (~VIRTIO_NET_S_LINK_UP);
>                                 PMD_DRV_LOG(ERR, "virtio-user port %u is down",
> @@ -235,11 +229,6 @@ virtio_user_read_dev_config(struct virtio_hw *hw, size_t offset,
>                         } else {
>                                 dev->net_status |= VIRTIO_NET_S_LINK_UP;
>                         }
> -                       if (fcntl(dev->vhostfd, F_SETFL,
> -                                       flags & ~O_NONBLOCK) == -1) {
> -                               PMD_DRV_LOG(ERR, "error clearing O_NONBLOCK flag");
> -                               return;
> -                       }
>                 } else if (dev->is_server) {
>                         dev->net_status &= (~VIRTIO_NET_S_LINK_UP);
>                         if (virtio_user_server_reconnect(dev) >= 0)
> --
> 2.25.1
>


-- 
Christian Ehrhardt
Senior Staff Engineer, Ubuntu Server
Canonical Ltd