From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:34245)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <kraxel@redhat.com>) id 1aM9zH-00039A-3S
	for qemu-devel@nongnu.org; Thu, 21 Jan 2016 02:48:59 -0500
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <kraxel@redhat.com>) id 1aM9zD-0003Bh-TU
	for qemu-devel@nongnu.org; Thu, 21 Jan 2016 02:48:59 -0500
Received: from mx1.redhat.com ([209.132.183.28]:34097)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <kraxel@redhat.com>) id 1aM9zD-0003Bb-OM
	for qemu-devel@nongnu.org; Thu, 21 Jan 2016 02:48:55 -0500
Message-ID: <1453362533.11655.26.camel@redhat.com>
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Thu, 21 Jan 2016 08:48:53 +0100
In-Reply-To: <20160120192229-mutt-send-email-mst@redhat.com>
References: <1452257883-19549-1-git-send-email-kraxel@redhat.com>
	<20160119123739.GA27855@thinpad.lan.raisama.net>
	<1453301733.11804.142.camel@redhat.com>
	<20160120153429.GA4218@thinpad.lan.raisama.net>
	<20160120171504.GB4218@thinpad.lan.raisama.net>
	<20160120192229-mutt-send-email-mst@redhat.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Mime-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH v2] pc: allow raising low memory via
 max-ram-below-4g option
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: Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>, Eduardo Habkost <ehabkost@redhat.com>, qemu-devel@nongnu.org

On Mi, 2016-01-20 at 19:25 +0200, Michael S. Tsirkin wrote:
> On Wed, Jan 20, 2016 at 03:15:04PM -0200, Eduardo Habkost wrote:
> > On Wed, Jan 20, 2016 at 01:34:29PM -0200, Eduardo Habkost wrote:
> > [...]
> > > Considering that we never supported
> > >   gigabyte_align && max_ram_below_4g > 3G ||
> > >   max_ram_below_4g > 3.5G
> > > before, we could simply remove the MachineClass::gigabyte_align
> > > field from pc_piix, and just do the following:
> > >=20
> > > * pc > 1.7: max_ram_below_4g =3D 3G
> > >   (equivalent to gigabyte_align=3Dtrue)
> > > * pc <=3D 1.7: max_ram_below_4g =3D 3.5G
> > >   (equivalent to gigabyte_align=3Dfalse)
> >=20
> > Ignore the suggestion above. I forgot that gigabyte_align applies
> > only if ram_size > 3.5GB (so setting max_ram_below_4g =3D 3G on
> > pc > 1.7 wouldn't work). So, unless somebody has a suggestion
> > that makes this logic simpler:
>=20
> I wonder whether we should just bite the bullet and ask management to
> maintain the physical memory map for us, instead of trying to give us
> hints.

I doubt this simplified things, given the backward compatibility
constrains we have.

cheers,
  Gerd