From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1NMPSz-0003J2-Mz for qemu-devel@nongnu.org; Sun, 20 Dec 2009 12:21:13 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1NMPSu-0003DX-Fb for qemu-devel@nongnu.org; Sun, 20 Dec 2009 12:21:12 -0500 Received: from [199.232.76.173] (port=54906 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1NMPSu-0003DU-8B for qemu-devel@nongnu.org; Sun, 20 Dec 2009 12:21:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:63980) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1NMPSt-0004sj-Q4 for qemu-devel@nongnu.org; Sun, 20 Dec 2009 12:21:08 -0500 Date: Sun, 20 Dec 2009 19:18:22 +0200 From: "Michael S. Tsirkin" Subject: Re: [Qemu-devel] cpuid problem in upstream qemu with kvm Message-ID: <20091220171822.GD31257@redhat.com> References: <4B2698A9.9090107@codemonkey.ws> <20091214200002.GA27769@redhat.com> <4B2699BB.1090302@codemonkey.ws> <20091214201049.GD6150@redhat.com> <4B269D99.8080404@codemonkey.ws> <4B2DF334.6030208@redhat.com> <20091220155101.GB31257@redhat.com> <4B2E49E5.6050709@redhat.com> <20091220165612.GC31257@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alexander Graf Cc: Avi Kivity , Gleb Natapov , qemu-devel@nongnu.org On Sun, Dec 20, 2009 at 06:17:02PM +0100, Alexander Graf wrote: > > On 20.12.2009, at 17:56, Michael S. Tsirkin wrote: > > > On Sun, Dec 20, 2009 at 05:59:33PM +0200, Avi Kivity wrote: > >> On 12/20/2009 05:51 PM, Michael S. Tsirkin wrote: > >>> > >>>> Maybe we should make -cpu host the default. That will give the best > >>>> performance for casual users, more testing for newer features, and will > >>>> force management apps to treat migration much more seriously. The > >>>> downside is that casual users upgrading their machines might experience > >>>> issues with Windows. Feature compatibility is not just about migration. > >>>> > >>> This seems very aggressive. Can't we whitelist features that we know > >>> about? Further, doesn't KVM already do this? > >>> > >>> > >> > >> It does, but without -cpuid host you're stuck with qemu64 (kvm.ko > >> doesn't add features userspace didn't request). > > > > Hmm, then, shouldn't either kvm or qemu mask features that we do not > > emulate well enough to make windows not crash? > > -cpu host does that already, no? > > Alex I expected so, but Avi here seems to say windows will crash if you use a new CPU with it ... -- MST