From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932125Ab2ISKOO (ORCPT ); Wed, 19 Sep 2012 06:14:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:25017 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756071Ab2ISKOM (ORCPT ); Wed, 19 Sep 2012 06:14:12 -0400 Message-ID: <50599AE2.80601@redhat.com> Date: Wed, 19 Sep 2012 13:13:54 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: Suresh Siddha CC: hpa@zytor.com, mingo@kernel.org, torvalds@linux-foundation.org, andreas.herrmann3@amd.com, bp@amd64.org, robert.richter@amd.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/6] x86, kvm: use kernel_fpu_begin/end() in kvm_load/put_guest_fpu() References: <1345842782-24175-1-git-send-email-suresh.b.siddha@intel.com> <1345842782-24175-4-git-send-email-suresh.b.siddha@intel.com> In-Reply-To: <1345842782-24175-4-git-send-email-suresh.b.siddha@intel.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/25/2012 12:12 AM, Suresh Siddha wrote: > kvm's guest fpu save/restore should be wrapped around > kernel_fpu_begin/end(). This will avoid for example taking a DNA > in kvm_load_guest_fpu() when it tries to load the fpu immediately > after doing unlazy_fpu() on the host side. > > More importantly this will prevent the host process fpu from being > corrupted. > > Signed-off-by: Suresh Siddha > Cc: Avi Kivity > --- > arch/x86/kvm/x86.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 42bce48..67e773c 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -5969,7 +5969,7 @@ void kvm_load_guest_fpu(struct kvm_vcpu *vcpu) > */ > kvm_put_guest_xcr0(vcpu); > vcpu->guest_fpu_loaded = 1; > - unlazy_fpu(current); > + kernel_fpu_begin(); > fpu_restore_checking(&vcpu->arch.guest_fpu); > trace_kvm_fpu(1); This breaks kvm, since it disables preemption. What we want here is to save the user fpu state if it was loaded, and do nothing if wasn't. Don't know what's the new API for that. > } > @@ -5983,6 +5983,7 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu) > > vcpu->guest_fpu_loaded = 0; > fpu_save_init(&vcpu->arch.guest_fpu); > + kernel_fpu_end(); > ++vcpu->stat.fpu_reload; > kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu); > trace_kvm_fpu(0); > -- error compiling committee.c: too many arguments to function