From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH] KVM: SVM: Add xsetbv intercept Date: Tue, 07 Dec 2010 11:34:33 +0200 Message-ID: <4CFDFFA9.5050804@redhat.com> References: <1291394523-7689-1-git-send-email-joerg.roedel@amd.com> <4CFD0B06.9010308@redhat.com> <20101206174852.GG4936@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: "Roedel, Joerg" Return-path: In-Reply-To: <20101206174852.GG4936@amd.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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). One more thing to watch out for. We also need to see if there aren't more mistakes like that out there. -- error compiling committee.c: too many arguments to function