linux-kernel - Re: [PATCH 06/11] virtio: blk: Add freeze, restore handlers to support S4

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Message-ID: <20111003091646.GA5192@amit-x200.redhat.com>
Date:	Mon, 3 Oct 2011 14:46:46 +0530
From:	Amit Shah <amit.shah@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/11] virtio: blk: Add freeze, restore handlers to
 support S4

On (Sun) 02 Oct 2011 [11:37:33], Michael S. Tsirkin wrote:
> On Thu, Sep 29, 2011 at 08:56:02PM +0530, Amit Shah wrote:
> > Delete the vq on the freeze callback to prepare for hibernation.
> > Re-create the vq in the restore callback to resume normal function.
> > 
> > Signed-off-by: Amit Shah <amit.shah@...hat.com>
> > ---
> >  drivers/block/virtio_blk.c |   17 +++++++++++++++++
> >  1 files changed, 17 insertions(+), 0 deletions(-)
> > 
> > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> > index 509760b..9844d2c 100644
> > --- a/drivers/block/virtio_blk.c
> > +++ b/drivers/block/virtio_blk.c
> > @@ -549,6 +549,19 @@ static void __devexit virtblk_remove(struct virtio_device *vdev)
> >  	kfree(vblk);
> >  }
> >  
> > +#ifdef CONFIG_PM
> > +static int virtblk_freeze(struct virtio_device *vdev)
> > +{
> > +	vdev->config->del_vqs(vdev);
> 
> What prevents the guest from trying to use the VQ while
> this is in progress? IF it does, what prevents a crash?

An oversight: Sasha pointed this out, too, and I've now fixed this by
adding a call to vdev->config->reset() before deleting vqs.

		Amit
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