From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48790) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZIOMf-0000vO-CJ for qemu-devel@nongnu.org; Thu, 23 Jul 2015 17:49:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZIOMb-0004C1-Iz for qemu-devel@nongnu.org; Thu, 23 Jul 2015 17:49:17 -0400 Received: from e17.ny.us.ibm.com ([129.33.205.207]:35569) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZIOMb-0004Bm-Ey for qemu-devel@nongnu.org; Thu, 23 Jul 2015 17:49:13 -0400 Received: from /spool/local by e17.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 23 Jul 2015 17:49:12 -0400 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable From: Michael Roth In-Reply-To: <20150723213819.15254.14516@loki> References: <1437566099-10004-1-git-send-email-lvivier@redhat.com> <1437675858-14070-1-git-send-email-lvivier@redhat.com> <1437684406.7562.62.camel@kernel.crashing.org> <20150724000923-mutt-send-email-mst@redhat.com> <20150723213819.15254.14516@loki> Message-ID: <20150723214902.15254.51200@loki> Date: Thu, 23 Jul 2015 16:49:02 -0500 Subject: Re: [Qemu-devel] [Qemu-ppc] [PATCH v2] pci: allow 0 address for PCI IO/MEM regions List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell , "Michael S. Tsirkin" Cc: Laurent Vivier , "qemu-ppc@nongnu.org" , QEMU Developers , David Gibson Quoting Michael Roth (2015-07-23 16:38:19) > Quoting Peter Maydell (2015-07-23 16:24:20) > > On 23 July 2015 at 22:19, Peter Maydell wrot= e: > > > On 23 July 2015 at 22:10, Michael S. Tsirkin wrote: > > >> On Thu, Jul 23, 2015 at 10:00:30PM +0100, Peter Maydell wrote: > > >>> (Also, none of our PCI device models actually try to do > > >>> the "BAR at zero means I won't respond" behaviour, which > > >>> presumably they might do in real life.) > > > > > >> Maybe some devices do this, but I'm guessing not all of them, > > >> since there's no hint in the pci spec that they should. > > > > > > I think this depends on which version of the spec you > > > read. > > = > > Bikeshedding about ancient specs aside, I think it's the > > bugs in the PC model's memory region priorities that > > are the real reason the special case of zero is sticking > > around. If we fixed those we should be able to drop it. > = > What's the intended fix? That legacy/platform regions > should hide any regions a guest attempts to map over it? nm, i see this was already covered :) I seem to recall Michael suggesting it may have already been fixed on x86. I think we had a TODO to figure out all the architectures that don't use IO windows and figure out if they need a fix as well. > = > > = > > -- PMM > > = > = >=20