From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753876Ab1JCJXo (ORCPT ); Mon, 3 Oct 2011 05:23:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:64604 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753258Ab1JCJXi (ORCPT ); Mon, 3 Oct 2011 05:23:38 -0400 Date: Mon, 3 Oct 2011 11:24:44 +0200 From: "Michael S. Tsirkin" To: Amit Shah Cc: Rusty Russell , linux-kernel@vger.kernel.org Subject: Re: [PATCH 06/11] virtio: blk: Add freeze, restore handlers to support S4 Message-ID: <20111003092443.GA16852@redhat.com> References: <5160f2cf536e7c506a5e90b4cb95e0f2e41c53d9.1317309123.git.amit.shah@redhat.com> <20111002093733.GE29706@redhat.com> <20111003091646.GA5192@amit-x200.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111003091646.GA5192@amit-x200.redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 03, 2011 at 02:46:46PM +0530, Amit Shah wrote: > 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 > > > --- > > > 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 This stops the host from accessing the VQ, but does not stop the *guest*.