[PATCH] virtio_mem: break device on remove

From: Michael S. Tsirkin
Date: Fri Jan 14 2022 - 16:43:35 EST


A common pattern for device reset is currently:
vdev->config->reset(vdev);
.. cleanup ..

reset prevents new interrupts from arriving and waits for interrupt
handlers to finish.

However if - as is common - the handler queues a work request which is
flushed during the cleanup stage, we have code adding buffers / trying
to get buffers while device is reset. Not good.

This was reproduced by running
modprobe virtio_console
modprobe -r virtio_console
in a loop, and this reasoning seems to apply to virtio mem though
I could not reproduce it there.

Fix this up by calling virtio_break_device + flush before reset.

Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
drivers/virtio/virtio_mem.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 38becd8d578c..33b8a118a3ae 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -2888,6 +2888,8 @@ static void virtio_mem_remove(struct virtio_device *vdev)
virtio_mem_deinit_hotplug(vm);

/* reset the device and cleanup the queues */
+ virtio_break_device(vdev);
+ flush_work(&vm->wq);
virtio_reset_device(vdev);
vdev->config->del_vqs(vdev);

--
MST