From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([208.118.235.92]:46036)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1TitQJ-0003sd-Mi
	for qemu-devel@nongnu.org; Wed, 12 Dec 2012 16:01:00 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1TitQD-0007E1-T9
	for qemu-devel@nongnu.org; Wed, 12 Dec 2012 16:00:59 -0500
Received: from mx1.redhat.com ([209.132.183.28]:63895)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1TitQD-0007Dx-Kv
	for qemu-devel@nongnu.org; Wed, 12 Dec 2012 16:00:53 -0500
Message-ID: <50C8F075.4000206@redhat.com>
Date: Wed, 12 Dec 2012 22:00:37 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
MIME-Version: 1.0
References: <20121212143038.GD15555@redhat.com> <50C8965A.7020004@redhat.com>
	<20121212144758.GF15555@redhat.com> <50C89C47.7040108@redhat.com>
	<20121212152508.GB16750@redhat.com> <50C8A855.4050607@redhat.com>
	<20121212163713.GD17446@redhat.com> <50C8B627.606@redhat.com>
	<20121212171423.GB18597@redhat.com> <50C8C143.2010503@redhat.com>
	<20121212192336.GA20201@redhat.com>
In-Reply-To: <20121212192336.GA20201@redhat.com>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCHv2] virtio: verify that all outstanding
	buffers are flushed
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: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, Anthony Liguori <aliguori@us.ibm.com>, Rusty Russell <rusty@rustcorp.com.au>, qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>

Il 12/12/2012 20:23, Michael S. Tsirkin ha scritto:
>>> Saving inuse counter is useless. We need to know which requests
>>> are outstanding if we want to retry them on remote.
>>
>> And that's what virtio-blk and virtio-scsi have been doing for years.
> 
> I don't see it - all I see in save is virtio_save.

static void virtio_blk_save(QEMUFile *f, void *opaque)
{
    VirtIOBlock *s = opaque;
    VirtIOBlockReq *req = s->rq;

    virtio_save(&s->vdev, f);
    
    while (req) {
        qemu_put_sbyte(f, 1);
        qemu_put_buffer(f, (unsigned char*)&req->elem, sizeof(req->elem));
        req = req->next;
    }
    qemu_put_sbyte(f, 0);
}


virtio-scsi does it in virtio_scsi_save_request.

> You need to retry A1 on remote. How do you do that? There's
> no way to find out it has not been completed
> from the ring itself.

virtio_blk_dma_restart_bh and scsi_dma_restart_bh do it.

Paolo