From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:43245) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RLOlH-0003SL-KM for qemu-devel@nongnu.org; Tue, 01 Nov 2011 20:33:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RLOlG-0005hn-Lt for qemu-devel@nongnu.org; Tue, 01 Nov 2011 20:32:59 -0400 Received: from mail-gy0-f173.google.com ([209.85.160.173]:63730) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RLOlG-0005hj-JM for qemu-devel@nongnu.org; Tue, 01 Nov 2011 20:32:58 -0400 Received: by gya6 with SMTP id 6so4239790gya.4 for ; Tue, 01 Nov 2011 17:32:58 -0700 (PDT) Message-ID: <4EB08FB6.3080108@codemonkey.ws> Date: Tue, 01 Nov 2011 19:32:54 -0500 From: Anthony Liguori MIME-Version: 1.0 References: <1317360376-12090-1-git-send-email-david@gibson.dropbear.id.au> <4EB07096.4070806@us.ibm.com> <20111102001658.GF5379@truffala.fritz.box> In-Reply-To: <20111102001658.GF5379@truffala.fritz.box> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] virtio: Add PCI memory BAR in addition to PIO BAR List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori , rusty@rustcorp.com.au, qemu-devel@nongnu.org On 11/01/2011 07:16 PM, David Gibson wrote: > On Tue, Nov 01, 2011 at 05:20:06PM -0500, Anthony Liguori wrote: >> On 09/30/2011 12:26 AM, David Gibson wrote: >>> Currently, virtio devices are usually presented to the guest as an >>> emulated PCI device, virtio_pci. Although the actual IO operations >>> are done through system memory, the configuration of the virtio device >>> is done through the one PCI IO space BAR that virtio_pci presents. >>> >>> But PCI IO space (aka PIO) is deprecated for modern PCI devices, and >>> on some systems with many PCI domains accessing PIO space can be >>> problematic. For example on the existing PowerVM implementation of >>> the PAPR spec, PCI PIO access is not supported at all. We're hoping >>> that our KVM implementation will support PCI PIO (once we support PCI >>> at all), but it will probably have some irritating limitations. >>> >>> This patch, therefore, extends the virtio_pci device to have a PCI >>> memory space (MMIO) BAR as well as the IO BAR. The MMIO BAR contains >>> exactly the same registers, in exactly the same layout as the existing >>> PIO BAR. >>> >>> Because the PIO BAR is still present, existing guest drivers should >>> still work fine. With this change in place, future guest drivers can >>> check for an MMIO BAR and use that if present (falling back to PIO >>> when possible to support older qemu versions). >>> >>> Signed-off-by: David Gibson >> >> Seems harmless for QEMU, so applied. You should update the >> virtio-pci spec too. > > Ugh, sorry. This is the old version of the patch which breaks when > you actually use it because it attempts to give proxy->bar two > different parents. I have a new version which does it correctly. > > So, do you want to revert and reapply, or should I just make a fix > patch? I'll revert. Thanks. Regards, Anthony Liguori