linux-kernel - Re: [PATCH] virtio_balloon: set DRIVER

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Message-ID: <877fuwjgqw.fsf@rustcorp.com.au>
Date:	Thu, 05 Mar 2015 13:24:47 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	"Michael S. Tsirkin" <mst@...hat.com>, linux-kernel@...r.kernel.org
Cc:	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH] virtio_balloon: set DRIVER_OK before using device

"Michael S. Tsirkin" <mst@...hat.com> writes:
> virtio spec requires that all drivers set DRIVER_OK
> before using devices. While balloon isn't yet
> included in the virtio 1 spec, previous spec versions
> also required this.
>
> virtio balloon might violate this rule: probe calls
> kthread_run before setting DRIVER_OK, which might run
> immediately and cause balloon to inflate/deflate.
>
> To fix, call virtio_device_ready before running the kthread.
>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>

Replied, CC'd stable.

Thanks,
Rusty.


> ---
>  drivers/virtio/virtio_balloon.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
> index 5a6ad6d..6a356e3 100644
> --- a/drivers/virtio/virtio_balloon.c
> +++ b/drivers/virtio/virtio_balloon.c
> @@ -508,6 +508,8 @@ static int virtballoon_probe(struct virtio_device *vdev)
>  	if (err < 0)
>  		goto out_oom_notify;
>  
> +	virtio_device_ready(vdev);
> +
>  	vb->thread = kthread_run(balloon, vb, "vballoon");
>  	if (IS_ERR(vb->thread)) {
>  		err = PTR_ERR(vb->thread);
> -- 
> MST
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