From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38724) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V6EKF-00019C-WC for qemu-devel@nongnu.org; Mon, 05 Aug 2013 02:31:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V6EK4-00022Z-CE for qemu-devel@nongnu.org; Mon, 05 Aug 2013 02:31:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:26591) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V6EK4-000225-4x for qemu-devel@nongnu.org; Mon, 05 Aug 2013 02:31:16 -0400 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r756VEfb006948 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 5 Aug 2013 02:31:14 -0400 Message-ID: <51FF46AF.50404@redhat.com> Date: Mon, 05 Aug 2013 08:31:11 +0200 From: Gerd Hoffmann MIME-Version: 1.0 References: <51FAB912.5040203@redhat.com> <51FB5672.4070907@redhat.com> <51FD5AE9.8090406@redhat.com> In-Reply-To: <51FD5AE9.8090406@redhat.com> Content-Type: text/plain; charset=ISO-8859-9 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] default slot used for vga device on q35 machines List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laine Stump Cc: Libvirt , Guannan Ren , qemu-devel@nongnu.org Hi, >>> 1) Is this difference intentional, or a bug? >> The vga simply goes into the first free slot. That happens to be #2 >> with i440fx and #1 with q35. > > It sounds like it's a safe bet to assume that -vga will put the device > on slot 2 for pc machinetypes and slot 1 for q35, no matter what other > devices there are, since -vga is always initialized first. Correct? Yes. > Do > you see any chance that might change in the future? (e.g. due to some > other new device that needs to be initialized even before vga) Highly unlikely. Also libvirt will switch over to use -device for vga cards, which will make this a moot point. >>> 3) Does the qxl multihead support really require that the device be at >>> slot 2 (as stated in the above bugzilla commend)? Or is that just a >>> misunderstanding/overstatement? >> It's not required at all. The problem is that on older qemu versions >> (pre-memory-api basically) it was impossible to create functional vga >> devices via -device due to an initialization order issue. Which implies >> you have to use -vga instead, which in turn implies the vga ends up in >> slot #2. On i440fx, but q35 didn't exist yet back then ;) > > Are you saying that it's still required to use -vga instead of -device > qxl-vga for pc machinetype? Or that it was needed at one time, but that > is no longer the case? If the latter, is there a reliable way to make > the decision whether or not we need to use -vga? libvirt has started using -device for vga cards, to be able to place them in any pci slot. IIRC it's used for qemu 1.1+ or 1.2+. That works fine for all vga cards except qxl. The bug which broke it for qxl will be fixed in 1.6 (and probably 1.5.3 too). cheers, Gerd