From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1Mvys3-0007xz-Rt
	for qemu-devel@nongnu.org; Thu, 08 Oct 2009 15:41:51 -0400
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1Mvyry-0007qw-Qy
	for qemu-devel@nongnu.org; Thu, 08 Oct 2009 15:41:51 -0400
Received: from [199.232.76.173] (port=42214 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1Mvyry-0007qm-Ly
	for qemu-devel@nongnu.org; Thu, 08 Oct 2009 15:41:46 -0400
Received: from mx1.redhat.com ([209.132.183.28]:33126)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <mst@redhat.com>) id 1Mvyry-0006Rp-78
	for qemu-devel@nongnu.org; Thu, 08 Oct 2009 15:41:46 -0400
Date: Thu, 8 Oct 2009 21:39:40 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] Re: [PATCH 2/3] qemu: make cirrus init value pci
	spec compliant
Message-ID: <20091008193939.GA18838@redhat.com>
References: <cover.1255013225.git.mst@redhat.com>
	<20091008145241.GC12275@redhat.com> <4ACE0559.5040206@redhat.com>
	<20091008160623.GA13710@redhat.com> <4ACE0FC6.3050908@redhat.com>
	<20091008184011.GA6576@shareable.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20091008184011.GA6576@shareable.org>
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Jamie Lokier <jamie@shareable.org>
Cc: Anthony Liguori <aliguori@us.ibm.com>, Avi Kivity <avi@redhat.com>, kvm-devel <kvm@vger.kernel.org>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

On Thu, Oct 08, 2009 at 07:40:12PM +0100, Jamie Lokier wrote:
> Avi Kivity wrote:
> > On 10/08/2009 06:06 PM, Michael S. Tsirkin wrote:
> > >On Thu, Oct 08, 2009 at 05:29:29PM +0200, Avi Kivity wrote:
> > >   
> > >>On 10/08/2009 04:52 PM, Michael S. Tsirkin wrote:
> > >>     
> > >>>PCI memory should be disabled at reset, otherwise
> > >>>we might claim transactions at address 0.
> > >>>I/O should also be disabled, although for cirrus
> > >>>it is harmless to enable it as we do not
> > >>>have I/O bar.
> > >>>
> > >>>Note: need bios fix for this patch to work:
> > >>>currently pc-bios incorrently assumes that it does not
> > >>>need to enable i/o unless device has i/o bar.
> > >>>
> > >>>Signed-off-by: Michael S. Tsirkin<mst@redhat.com>
> > >>
> > >>This needs to be conditional on the machine type.  Old machines must
> > >>retain this code for live migration to work (we need to live migrate the
> > >>bios, so we can't assume the bios fix is in during live migration from
> > >>older qemus).
> > >>     
> > >No, if you migrate from older qemu you will be fine as command
> > >is enabled there on init.
> > >   
> > 
> > Right.
> 
> No, I think Avi was right the first time.
> 
> Migrating from an older qemu will be fine at first, but at the next
> reset _following_ migration, it'll be running the old BIOS on a new
> qemu and fail.

OK but Avi was commenting on the patch that removed bit set in init,
ignoring reset behaviour.
So for old BIOS we want a flag not to clear I/O enable bit
on reset for VGA devices.


> -- Jamie