From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:39213)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <mst@redhat.com>) id 1akuAW-0004eS-Bg
	for qemu-devel@nongnu.org; Tue, 29 Mar 2016 09:58:53 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <mst@redhat.com>) id 1akuAS-0007WY-Aq
	for qemu-devel@nongnu.org; Tue, 29 Mar 2016 09:58:52 -0400
Date: Tue, 29 Mar 2016 16:58:34 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20160329165700-mutt-send-email-mst@redhat.com>
References: <1459258923-10319-1-git-send-email-mst@redhat.com>
	<1459258923-10319-3-git-send-email-mst@redhat.com>
	<56FA8982.2000404@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <56FA8982.2000404@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 2/2] virtio-blk: use aio handler for data
	plane
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>, Kevin Wolf <kwolf@redhat.com>, qemu-block@nongnu.org, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

On Tue, Mar 29, 2016 at 03:56:18PM +0200, Paolo Bonzini wrote:
> 
> 
> On 29/03/2016 15:42, Michael S. Tsirkin wrote:
> > @@ -262,6 +274,7 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
> >  
> >      /* Stop notifications for new requests from guest */
> >      virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx, false, false);
> 
> I think that this should have been ", true, false" even before your
> patch; I'd prefer to fix it even if the problem is latent.

Makes sense - post a patch?

> The patch looks good, and it might even be an API improvement
> independent of Conny's patches.  The reentrancy _is_ hard to understand,
> and eliminating it makes the new API not just a hack.
> 
> In that case I would unify the new function with
> virtio_queue_aio_set_host_notifier_handler.  In other words
> 
> - virtio_queue_aio_set_host_notifier_handler(vq, ctx, NULL) is
> the same as
> 
>      virtio_set_queue_aio(s->vq, NULL);
>      virtio_queue_aio_set_host_notifier_handler(vq, ctx, true, false);
> 
> - virtio_queue_aio_set_host_notifier_handler(vq, ctx, fn) is the same as
> 
>      virtio_queue_aio_set_host_notifier_handler(vq, ctx, true, true);
>      virtio_set_queue_aio(vq, fn);
> 
> Thanks,
> 
> Paolo

In that case, we'll have to also change scsi to use the new API.
A bit more work, to be sure.
Does scsi have the same problem as blk?

> > +    virtio_set_queue_aio(s->vq, NULL);
> >  
> >      /* Drain and switch bs back to the QEMU main loop */
> >      blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context());