From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:35169)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <marcel.a@redhat.com>) id 1WXALB-0007mI-2h
	for qemu-devel@nongnu.org; Mon, 07 Apr 2014 10:16:07 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <marcel.a@redhat.com>) id 1WXAL1-0008QS-Um
	for qemu-devel@nongnu.org; Mon, 07 Apr 2014 10:16:01 -0400
Received: from mx1.redhat.com ([209.132.183.28]:48573)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <marcel.a@redhat.com>) id 1WXAL1-0008QD-Bc
	for qemu-devel@nongnu.org; Mon, 07 Apr 2014 10:15:51 -0400
Message-ID: <1396880173.10570.25.camel@localhost.localdomain>
From: Marcel Apfelbaum <marcel.a@redhat.com>
Date: Mon, 07 Apr 2014 17:16:13 +0300
In-Reply-To: <20140407140901.GB16907@redhat.com>
References: <1396868342-12005-1-git-send-email-marcel.a@redhat.com>
	<20140407121508.GD16369@redhat.com>
	<1396874646.5001.76.camel@nilsson.home.kraxel.org>
	<20140407133415.GB16541@redhat.com>
	<1396878714.10570.18.camel@localhost.localdomain>
	<20140407140901.GB16907@redhat.com>
Content-Type: text/plain; charset="UTF-8"
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [SeaBIOS] [PATCH] hw/pci: reserve IO and mem for
 pci-2-pci bridges with no devices attached
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: kevin@koconnor.net, seabios@seabios.org, Gerd Hoffmann <kraxel@redhat.com>, qemu-devel@nongnu.org

On Mon, 2014-04-07 at 17:09 +0300, Michael S. Tsirkin wrote:
> On Mon, Apr 07, 2014 at 04:51:54PM +0300, Marcel Apfelbaum wrote:
[...]
> > > > I don't think we'll need that for the SHPC bridge.
> > > 
> > > Why not?
> > Because "has shpc" => not an PCIe port. (as far as I know)
> > Anyway, why have shpc capability but no I/O or mem to support it?
^^^
[...]
> 
> 
> AFAIK the spec does not list reset value for this register.
> IIRC QEMU resets both to 0.
Thanks, what do you think about the above ? ^^^
While I am not against it, it seems redundant.
It has shpc => it needs I/O or mem space.

Marcel

> 
> 
> > > 	- read back value
> > > 
> > > value 0 means bridge does not support I/O.
> > > 
> > > 
> > > A similar trick should work for other optional resources.
> > > 
> > > 
> > > > For express it indeed makes sense to avoid claiming IO address space.
> > > > I'd try to find something more automatic though, where you don't need
> > > > some kind of "disable io for this express port" config option.
> > > 
> > > Won't same trick as above work?
> > > 
> > > > For express ports which can only have a single device underneath we can
> > > > check whenever we have a device and if one is present already don't
> > > > bother claiming extra resources for hotplug.
> > > > 
> > > > > > +    for (cap = pci_config_readb(pci->bdf, PCI_CAPABILITY_LIST); cap;
> > > > > > +                cap = pci_config_readb(pci->bdf, cap + PCI_CAP_LIST_NEXT))
> > > > > > +        if (pci_config_readb(pci->bdf, cap + PCI_CAP_LIST_ID) == cap_id)
> > > > > > +            return cap;
> > > > > 
> > > > > I would also limit this to 256 iterations, to make sure
> > > > > we dont' get into an infinite loop with a broken device.
> > > > 
> > > > Good point.
> > > > 
> > > > cheers,
> > > >   Gerd
> > > > 
> > 
> >