From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757329Ab1KQM32 (ORCPT ); Thu, 17 Nov 2011 07:29:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58279 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757094Ab1KQM30 (ORCPT ); Thu, 17 Nov 2011 07:29:26 -0500 Date: Thu, 17 Nov 2011 17:59:20 +0530 From: Amit Shah To: "Michael S. Tsirkin" Cc: Rusty Russell , Virtualization List , levinsasha928@gmail.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 11/11] virtio: balloon: Add freeze, restore handlers to support S4 Message-ID: <20111117122920.GB2873@amit-x200.redhat.com> References: <1147d4f726e51f2e03a84f3732d60ccd0d8e480c.1321530505.git.amit.shah@redhat.com> <20111117122508.GB19682@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111117122508.GB19682@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 (Thu) 17 Nov 2011 [14:25:08], Michael S. Tsirkin wrote: > On Thu, Nov 17, 2011 at 05:27:42PM +0530, Amit Shah wrote: > > Delete the vqs on the freeze callback to prepare for hibernation. > > Re-create the vqs in the restore callback to resume normal function. > > > > Signed-off-by: Amit Shah > > --- > > drivers/virtio/virtio_balloon.c | 20 ++++++++++++++++++++ > > 1 files changed, 20 insertions(+), 0 deletions(-) > > > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > > index 1ff3cf4..90149d1 100644 > > --- a/drivers/virtio/virtio_balloon.c > > +++ b/drivers/virtio/virtio_balloon.c > > @@ -363,6 +363,22 @@ static void __devexit virtballoon_remove(struct virtio_device *vdev) > > kfree(vb); > > } > > > > +#ifdef CONFIG_PM > > +static int virtballoon_freeze(struct virtio_device *vdev) > > +{ > > + /* Now we reset the device so we can clean up the queues. */ > > + vdev->config->reset(vdev); > > + > > This is a weird thing to do. We normally delete vqs then reset. No, all the drivers first reset, then delete. > For example, I don't know whether we guarantee what happens > to MSI-X vectors assigned meanwhile if you reset. > IIRC qemu doesn't use MSI-X for the balloon, but nothing > prevents it. > > > + vdev->config->del_vqs(vdev); > > What prevents requests being submitted at this point? > I see all kind of handling of freezing in the balloon thread ... > maybe that gives us some guarantees, but if yes > it makes sense to add a comment to point this out. Once reset, the host won't write anything to the vqs anyway.. Amit