linux-kernel - [PATCH 4/4] virtio_net: fix virtnet_send_command() with vdpa_sim

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Date:   Sun, 22 Jan 2023 11:05:26 +0100
From:   Laurent Vivier <lvivier@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Parav Pandit <parav@...dia.com>,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        Eli Cohen <elic@...dia.com>, Jason Wang <jasowang@...hat.com>,
        Gautam Dawar <gautam.dawar@...inx.com>,
        Cindy Lu <lulu@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eugenio Pérez <eperezma@...hat.com>
Subject: [PATCH 4/4] virtio_net: fix virtnet_send_command() with vdpa_sim_net

virtnet_send_command() sends a command to the control virtqueue
by adding the command to the virtqueue, kicking the queue and waiting
in a loop.

The vdpa simulator simulates the control virqueue using a work queue:
the virqueue_kick() calls schedule_work() to start the queue processing.
But as virtnet_send_command() uses a loop, the scheduler cannot schedule
the workqueue and the virtqueue is never processed (and the command
never executed).

To fix that, replace in the loop the cpu_relax() by a schedule().

Signed-off-by: Laurent Vivier <lvivier@...hat.com>
---
 drivers/net/virtio_net.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 29b3cc72082d..546c0b2baaca 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -2011,7 +2011,7 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
 	while (!virtqueue_get_buf(vi->cvq, &tmp) &&
 	       !virtqueue_is_broken(vi->cvq) &&
 	       !time_after(jiffies, timeout))
-		cpu_relax();
+		schedule();
 
 	return vi->ctrl->status == VIRTIO_NET_OK;
 }
-- 
2.39.0