From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([208.118.235.92]:56934)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1S89Gq-0006pR-7K
	for qemu-devel@nongnu.org; Thu, 15 Mar 2012 07:55:19 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1S89Ga-0005XS-IQ
	for qemu-devel@nongnu.org; Thu, 15 Mar 2012 07:55:03 -0400
Received: from mx1.redhat.com ([209.132.183.28]:47674)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <pbonzini@redhat.com>) id 1S89Ga-0005Ww-A0
	for qemu-devel@nongnu.org; Thu, 15 Mar 2012 07:54:48 -0400
Message-ID: <4F61D877.5080600@redhat.com>
Date: Thu, 15 Mar 2012 12:54:31 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
MIME-Version: 1.0
References: <1331802150-12183-1-git-send-email-dmitry.fleytman@ravellosystems.com>
	<CAJSP0QWGb+n3hmBp37N_Mahtopqw+wieKFi+6a3wsZ4bswZPLA@mail.gmail.com>
In-Reply-To: <CAJSP0QWGb+n3hmBp37N_Mahtopqw+wieKFi+6a3wsZ4bswZPLA@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH 0/5] VMWare PVSCSI paravirtual device
	implementation
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: Stefan Hajnoczi <stefanha@gmail.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, Alex Fishman <alex.fishman@ravellosystems.com>, "Michael S. Tsirkin" <mst@redhat.com>, yvugenfi@redhat.com, Izik Eidus <izik.eidus@ravellosystems.com>, qemu-devel@nongnu.org, Dmitry Fleytman <dmitry.fleytman@ravellosystems.com>

Il 15/03/2012 12:47, Stefan Hajnoczi ha scritto:
> What is the V2V strategy?
> 
> Supporting these devices is fine if we have a way to convert guests to
> use virtio.  But if the plan is to keep the guests on VMware pv
> devices, then that will split the development effort on support and
> optimizing I/O devices.  All the performance work going into
> virtio-net (vhost-net), virtio-blk, and possibly virtio-scsi isn't
> easy to duplicate for VMware pv devices.  Also, we cannot extend
> VMware devices easily while retaining compatibility.

virtio-scsi and vmware-pvscsi should be equivalent in terms of
performance.  Of course vhost-scsi would be another story.

I think supporting these devices is good anyway as long as they are
expected to perform decently but not necessarily as well as virtio.
After all we do support both vmware-vga and qxl.

> I'm for supporting these devices, but we really need another step to
> move migrated guests onto virtio - otherwise users will be
> disappointed with KVM's support/performance.  Can you explain a bit
> how you want these devices to be used?

I'm curious about this too.

Paolo