From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34446) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z4Pez-0003ae-9u for qemu-devel@nongnu.org; Mon, 15 Jun 2015 04:22:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z4Pev-0006Yj-W4 for qemu-devel@nongnu.org; Mon, 15 Jun 2015 04:22:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33205) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z4Pev-0006YW-QM for qemu-devel@nongnu.org; Mon, 15 Jun 2015 04:22:21 -0400 Date: Mon, 15 Jun 2015 10:22:17 +0200 From: "Michael S. Tsirkin" Message-ID: <20150615102126-mutt-send-email-mst@redhat.com> References: <557AA59E.6050509@redhat.com> <20150612130326.GA3622@morn.localdomain> <557AFE80.4040402@redhat.com> <20150612184009.GA3963@morn.localdomain> <20150614140322-mutt-send-email-mst@redhat.com> <20150614145022.GC10633@morn.localdomain> <20150614195525-mutt-send-email-mst@redhat.com> <1434317958.3803.38.camel@kernel.crashing.org> <20150614215955.GA6017@morn.localdomain> <1434336608.3803.45.camel@kernel.crashing.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1434336608.3803.45.camel@kernel.crashing.org> Subject: Re: [Qemu-devel] [PATCH V2] pci: fixes to allow booting from extra root pci buses. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Benjamin Herrenschmidt Cc: seabios@seabios.org, qemu-devel@nongnu.org, Kevin O'Connor , Gerd Hoffmann , Marcel Apfelbaum , Laszlo Ersek On Mon, Jun 15, 2015 at 12:50:08PM +1000, Benjamin Herrenschmidt wrote: > On Sun, 2015-06-14 at 17:59 -0400, Kevin O'Connor wrote: > > There are x86 systems with multiple separate PCI root buses where one > > can access the pci config space of all the buses using the same 0x0cf8 > > IO space. During system setup, the multiple PCI root buses are each > > configured to only respond to PCI config accesses within its range of > > bus numbers. So if "root1" is configured for bus ids between 64-128, > > then it will only forward the request if the bus id in the request is > > between 64-128. > > > > I suspect in your PPC example that the separate root buses all had > > separate io/memory space as well and thus were completely separate. > > (That is, they don't share the equivalent of IO 0x0cf8.) If so, > > that's different from how the x86 qemu code and the x86 systems I was > > discussing above work. > > Correct, my point is that qemu shouldn't be made to rely on the stable > bus numbers. Why not use the mmconfig address instead ? These are traditional pci buses, so they don't have an mmconfig. > That way you can > factor the bus number in via an offset if it's relevant or provide a > completely different address if the busses are separate. > > Ben. >