From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:59538) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RxE1P-0003gY-5Z for qemu-devel@nongnu.org; Tue, 14 Feb 2012 03:46:03 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RxE1J-0004Go-D6 for qemu-devel@nongnu.org; Tue, 14 Feb 2012 03:45:59 -0500 Received: from fmmailgate02.web.de ([217.72.192.227]:38645) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RxE1I-0004GS-VH for qemu-devel@nongnu.org; Tue, 14 Feb 2012 03:45:53 -0500 Received: from moweb001.kundenserver.de (moweb001.kundenserver.de [172.19.20.114]) by fmmailgate02.web.de (Postfix) with ESMTP id 647BA1C186946 for ; Tue, 14 Feb 2012 09:45:51 +0100 (CET) Message-ID: <4F3A1F3B.9040204@web.de> Date: Tue, 14 Feb 2012 09:45:47 +0100 From: Jan Kiszka MIME-Version: 1.0 References: In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig82DA77441C733CAD3C38ECFF" Subject: Re: [Qemu-devel] Kernel mode VGAs? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gerhard Wiesinger Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig82DA77441C733CAD3C38ECFF Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 2012-02-14 08:12, Gerhard Wiesinger wrote: > Hello, >=20 > Current QEMU-KVM VGA implementation have the following problem with > legacy OS (e.g. DOS with INT10h calls): Performance is low on accessing= > A000:0 > page and doing bank switching at the 64k page. Do we already understand the mode and access patterns here? Which VGA adapter? Cirrus, standard, or any? What is the concrete test case (one that won't require me digging for MS Dose floppy disks in my basement)? >=20 > Would a kernel mode VGA solve these problems? > How complicated is it? > Is it possible to have only some parts in kernel mode? > Any further ideas or suggestions? Provided we take heavy exits so far, in-kernel acceleration may reduce the exit overhead by factor, hmm, maybe 3-4. Better is to avoid exists completely, i.e. switch the region to RAM mode. But that depends on the graphic mode, and I'm afraid we have already covered all which can be mapped like this. In any case, before discussing solutions, we need to analyze the problem.= Jan --------------enig82DA77441C733CAD3C38ECFF Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk86HzsACgkQitSsb3rl5xSPnwCgyl4ddr3r+7NdpZgtibmXM0kn KiUAn0acMJD4EP6to77jUmjIx8MdVb4h =rOEq -----END PGP SIGNATURE----- --------------enig82DA77441C733CAD3C38ECFF--