From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Roedel, Joerg" Subject: Re: [PATCH] KVM: SVM: Add xsetbv intercept Date: Tue, 7 Dec 2010 17:12:11 +0100 Message-ID: <20101207161211.GD13125@amd.com> References: <1291394523-7689-1-git-send-email-joerg.roedel@amd.com> <4CFD0B06.9010308@redhat.com> <20101206174852.GG4936@amd.com> <4CFDFFA9.5050804@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Cc: Marcelo Tosatti , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: Avi Kivity Return-path: Content-Disposition: inline In-Reply-To: <4CFDFFA9.5050804@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Tue, Dec 07, 2010 at 04:34:33AM -0500, Avi Kivity wrote: > On 12/06/2010 07:48 PM, Roedel, Joerg wrote: > > On Mon, Dec 06, 2010 at 11:10:46AM -0500, Avi Kivity wrote: > > > On 12/03/2010 06:42 PM, Joerg Roedel wrote: > > > > This patch implements the xsetbv intercept to the AMD part > > > > of KVM. This makes AVX usable in a save way for the guest on > > > > AVX capable AMD hardware. > > > > The patch is tested by using AVX in the guest and host in > > > > parallel and checking for data corruption. I also used the > > > > KVM xsave unit-tests and they all pass. > > > > > > > > > > That is really strange. You didn't need to do anything to get cpuid.avx > > > recognized. So running an older kvm on newer hardware will happily > > > expose avx even though it's not supported. > > > > > > We screwed up - we should have made cpuid.avx dependent on vendor support. > > > > Hmm, right. The set_supported_cpuid arch-callback should basically > > disable xsave on AMD for all KVM versions which do not handle the xsetbv > > intercept. > > > > Please post a patch to do that, and update this patch to undo the > change. We'll backport the first patch to -stable so that people > running older kernels don't get a nasty surprise when they upgrade their > hardware (and use -cpu host). Ok, I'll post them soon. -- AMD Operating System Research Center Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach General Managers: Alberto Bozzo, Andrew Bowd Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632