From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:38537) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QWMpr-0003KW-Fh for qemu-devel@nongnu.org; Tue, 14 Jun 2011 02:10:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QWMpp-0006L5-Og for qemu-devel@nongnu.org; Tue, 14 Jun 2011 02:10:47 -0400 Received: from fmmailgate02.web.de ([217.72.192.227]:39597) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QWMpp-0006Kc-3C for qemu-devel@nongnu.org; Tue, 14 Jun 2011 02:10:45 -0400 Message-ID: <4DF6FB62.60705@web.de> Date: Tue, 14 Jun 2011 08:10:42 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <4DF33413.9070605@web.de> <4DF5CE2E.50008@redhat.com> In-Reply-To: <4DF5CE2E.50008@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigE14385714DA5445D7A59AC37" Sender: jan.kiszka@web.de Subject: Re: [Qemu-devel] [PATCH][uq/master] kvm: x86: Save/restore FPU OP, IP and DP List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: Christophe Fergeau , Marcelo Tosatti , qemu-devel , kvm , Stefan Hajnoczi This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigE14385714DA5445D7A59AC37 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable On 2011-06-13 10:45, Avi Kivity wrote: > On 06/11/2011 12:23 PM, Jan Kiszka wrote: >> From: Jan Kiszka >> >> These FPU states are properly maintained by KVM but not yet by TCG. So= >> far we unconditionally set them to 0 in the guest which may cause >> state corruptions - not only during migration. >> >> >> -#define CPU_SAVE_VERSION 12 >> +#define CPU_SAVE_VERSION 13 >> >=20 > Incrementing the version number seems excessive - I can't imagine a > real-life guest will break due to fp pointer corruption >=20 > However, I don't think we have a mechanism for optional state. We > discussed this during the 18th VMState Subsection Symposium and IIRC > agreed to re-raise the issue when we encountered it, which appears to b= e > now. >=20 Whatever we invent, it has to be backported as well to allow that infamous traveling back in time, migrating VMs from newer to older versio= ns. Would that backporting be simpler if we used an unconditional subsection for the additional states? Jan --------------enigE14385714DA5445D7A59AC37 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.15 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org/ iEYEARECAAYFAk32+2IACgkQitSsb3rl5xTEnACgpTYmSwX8AolOccXo1itfP/mf 0BIAnAj0OtoSy7XJfII3voAwlvB/3x0V =qDa5 -----END PGP SIGNATURE----- --------------enigE14385714DA5445D7A59AC37--