From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:51328) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RpgEH-0000YI-5E for qemu-devel@nongnu.org; Tue, 24 Jan 2012 08:16:09 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RpgEA-00031v-Ak for qemu-devel@nongnu.org; Tue, 24 Jan 2012 08:16:05 -0500 Received: from mail-iy0-f173.google.com ([209.85.210.173]:45145) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RpgEA-00031l-7Z for qemu-devel@nongnu.org; Tue, 24 Jan 2012 08:15:58 -0500 Received: by iahk25 with SMTP id k25so4561593iah.4 for ; Tue, 24 Jan 2012 05:15:57 -0800 (PST) Message-ID: <4F1EAF09.3030105@codemonkey.ws> Date: Tue, 24 Jan 2012 07:15:53 -0600 From: Anthony Liguori MIME-Version: 1.0 References: <4F19AB66.8060901@siemens.com> <4F1D4974.4090003@siemens.com> <4F1D4E43.7000501@siemens.com> <4F1D80BA.1040504@siemens.com> <4F1D9546.4040801@siemens.com> <4F1D9649.1000102@codemonkey.ws> <4F1E91AF.9040402@redhat.com> <4F1E959F.4060001@redhat.com> <4F1E96BA.40801@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v4 0/6] save/restore on Xen List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefano Stabellini Cc: "xen-devel@lists.xensource.com" , Jan Kiszka , "qemu-devel@nongnu.org" , Gerd Hoffmann , Paolo Bonzini , Avi Kivity On 01/24/2012 05:52 AM, Stefano Stabellini wrote: > On Tue, 24 Jan 2012, Avi Kivity wrote: >> On 01/24/2012 01:27 PM, Paolo Bonzini wrote: >>> On 01/24/2012 12:10 PM, Avi Kivity wrote: >>>>> But viewing RAM as just another device, having Xen only restore a >>>>> subset of devices should be a reasonable thing to do moving forward. >>>>> The main problem here I believe is that we have part of the VGA Bios >>>>> functionality in the hardware emulation. >>>> >>>> Doesn't the main BIOS clear the screen first thing at boot? Not even >>>> sure the reset is needed. >>> >>> Clearing the screen should only write to the RAM at 0xB8000 (and >>> perhaps 0xA0000 since IIRC it's where text-mode fonts lie). The >>> option ROM cannot even assume that the main BIOS knows about the VESA >>> framebuffer, can it? >> >> Yes, but why should anything else be needed? >> >> When you switch to a graphics mode, clear as much of the framebuffer as >> you need. > > After installing Win2K, I managed to reproduce the issue with the old > qemu-xen and rombios (removing the memset in the vga emulator). > However I cannot reproduce the issue with upstream qemu and seabios > (even if I remove the memset). > > I think that the memset was a workaround a bug in rombios, hence it is > not needed anymore. > > Removing the cirrus_vga memset would solve the main issue we have left > with save/restore on Xen. > However it wouldn't solve the problem for QXL: as Gerd pointed out, QXL > needs a reset to initialize some memory regions, so another "if we are > restoring don't do that" would be required to make it work on Xen... I believe this is a bug in QXL (or misdesign). It should move this logic into the VGA Bios. Regards, Anthony Liguori