From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NMczx-0000Sh-P0 for qemu-devel@nongnu.org; Mon, 21 Dec 2009 02:48:09 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NMczt-0000Qd-99 for qemu-devel@nongnu.org; Mon, 21 Dec 2009 02:48:09 -0500 Received: from [199.232.76.173] (port=35455 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NMczs-0000QO-3e for qemu-devel@nongnu.org; Mon, 21 Dec 2009 02:48:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:14785) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NMczr-000206-OR for qemu-devel@nongnu.org; Mon, 21 Dec 2009 02:48:04 -0500 Date: Mon, 21 Dec 2009 09:48:00 +0200 From: Gleb Natapov Subject: Re: [Qemu-devel] cpuid problem in upstream qemu with kvm Message-ID: <20091221074800.GV4490@redhat.com> References: <20091220155101.GB31257@redhat.com> <4B2E49E5.6050709@redhat.com> <20091220165612.GC31257@redhat.com> <20091220171822.GD31257@redhat.com> <20091220172341.GB21163@redhat.com> <2162E312-0110-42E1-A391-D75A6F013554@suse.de> <20091220173702.GC21163@redhat.com> <4B2E660F.1050703@codemonkey.ws> <04509ED0-8B29-4013-ACDC-AD3D28974433@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <04509ED0-8B29-4013-ACDC-AD3D28974433@suse.de> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: "Michael S. Tsirkin" , qemu-devel@nongnu.org, Avi Kivity On Sun, Dec 20, 2009 at 07:06:03PM +0100, Alexander Graf wrote: > > On 20.12.2009, at 18:59, Anthony Liguori wrote: > > > Gleb Natapov wrote: > >> Windows is a mystery box, so we can speculate as much as we want about it. > >> If you don't like something just say "it may break Windows" :) Losing > >> activation does sound like an issue too. > >> > > > > Downgrading seems more likely to cause problems. Considering running mplayer in a guest. If it detects SSE3 in one host and migrate to another host that doesn't have SSE3, you'll be running an instruction stream that uses instructions the processor doesn't support resulting in the application faulting due to an illegal operation. > > Yeah, migration with -cpu host doesn't sound like a sane thing to do. > > > KVM's cpuid filter doesn't help here because it won't attempt to mask things like sse3. It would be insane to emulate sse3 too. > > Well, I wouldn't be too sure on that one. Software may use SSE3 instructions to access MMIO in which case we do have to emulate it. Unfortunately this is already a reality. Look here: http://groups.google.com/group/linux.kernel/browse_thread/thread/ada9fa2d2574a8af -- Gleb.