From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49646) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V6MKn-0007ZJ-Ui for qemu-devel@nongnu.org; Mon, 05 Aug 2013 11:04:38 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V6MKi-00065k-Mi for qemu-devel@nongnu.org; Mon, 05 Aug 2013 11:04:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:30866) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V6MKi-000659-DY for qemu-devel@nongnu.org; Mon, 05 Aug 2013 11:04:28 -0400 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r75F4QoV026374 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Mon, 5 Aug 2013 11:04:26 -0400 Message-ID: <51FFBEF8.2040308@redhat.com> Date: Mon, 05 Aug 2013 09:04:24 -0600 From: Eric Blake 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: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="CbnJxWAXkOmmFOrNPILF7IR5m9fIS0qaB" 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, Gerd Hoffmann This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --CbnJxWAXkOmmFOrNPILF7IR5m9fIS0qaB Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 08/03/2013 01:32 PM, Laine Stump wrote: >>> >>> 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. >=20 >=20 > 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? 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) Any future qemu will be new enough to not require the use of -vga, so we only have to worry about the behavior of 1.5 and earlier with regards to placement of -vga. >=20 >=20 >> >>> 2) If it's intentional, will the device always be at slot 1 (and trig= ger >>> an error if something else is also placed at slot 1), or is it just >>> picking the first unused slot? (that would *not* be good, because we >>> must be able to predict what device is in which slot and prevent them= >>> from changing from run to run). >> The vga is the very first (pci) device being created (when selecting v= ia >> -vga), so it gets the slots mentioned above no matter what, even thoug= h >> simply picking the first unused slot. >> >>> 3) Does the qxl multihead support really require that the device be a= t >>> 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 impli= es >> 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 ;) >=20 > 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? Regarding the decision on whether to use -device or -vga, our hands are tied. With qemu 1.5 or earlier, we HAVE to use -vga, where spice initialization had a bug such that use of -device would not display the mouse. That bug has been fixed for qemu 1.6, so for qemu 1.6, we prefer to use -device. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --CbnJxWAXkOmmFOrNPILF7IR5m9fIS0qaB Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.13 (GNU/Linux) Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJR/774AAoJEKeha0olJ0NqL+IIAKdNlA5wOEp7M2PrWiCIvCaZ juvMlGquQ0knaWu8O24TfM6uU40bBzATEN0A85JJ0Gq6EvCam2/LhP04ayEdj6wU pSot8gQ/VtIF1wd9XaLBWkPlxUbxNVb+AENGAhRU3pn5oHSR1qUFTnXUomXWCbvO 5IQoYozjdyWWibfWE8KS8KOB+X68BSznyQglATCJF08acml4fUin0mOqnY0Dm6+k jP6+vbFSVxG6+qj1MFGgjTlq1fM2Rf8rqfPEVIG6WgynAqZyg1VsoC4sAMa+eKle x5bnSMieXilASjmzC9yCZ5X6M/Tu+MQ8ByNp0hd9cSqW3fdJN852flpbUEVLkl4= =uk1f -----END PGP SIGNATURE----- --CbnJxWAXkOmmFOrNPILF7IR5m9fIS0qaB--