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

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

[Yuan Wang]

[ upstream commit 41f9a1757ffc010cc3debaad9a56af8ad88d0c6d ]

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

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

[Christian Ehrhardt]

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