From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754688AbaLBIzS (ORCPT ); Tue, 2 Dec 2014 03:55:18 -0500 Received: from mail-wg0-f50.google.com ([74.125.82.50]:54556 "EHLO mail-wg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751519AbaLBIzP (ORCPT ); Tue, 2 Dec 2014 03:55:15 -0500 Message-ID: <547D7E6D.6090000@redhat.com> Date: Tue, 02 Dec 2014 09:55:09 +0100 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 Newsgroups: gmane.linux.kernel,gmane.comp.emulators.kvm.devel To: Wanpeng Li CC: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] kvm: x86: revert mask out xsaves References: <1417500894-7604-1-git-send-email-wanpeng.li@linux.intel.com> In-Reply-To: <1417500894-7604-1-git-send-email-wanpeng.li@linux.intel.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/12/2014 07:14, Wanpeng Li wrote: > xsaves will be exported to guest in the next patch, so revert the > mask out xsaves patch. > > Signed-off-by: Wanpeng Li > --- > arch/x86/kvm/cpuid.c | 10 +--------- > 1 file changed, 1 insertion(+), 9 deletions(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index a4f5ac4..7af07571 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -320,10 +320,6 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, > F(ADX) | F(SMAP) | F(AVX512F) | F(AVX512PF) | F(AVX512ER) | > F(AVX512CD); > > - /* cpuid 0xD.1.eax */ > - const u32 kvm_supported_word10_x86_features = > - F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1); Every single bit needs to be whitelisted independently of the others, so a full revert is not possible. We need to be careful about post-Skylake processors introducing new bits in this cpuid leaf. Also, you cannot just add F(XSAVES) here; you must only do it if XSAVES is actually supported. This makes sure that nested virtualization will _not_ present XSAVES to the guests until specific support is introduced for XSAVES and XRSTORS exits (including the XSS exit bitmap). In order to do this, you have to introduce a new member in kvm_x86_ops, modeling what was done for MPX. The second patch can then implement this new member. Thanks, Paolo > /* all calls to cpuid_count() should be made on the same cpu */ > get_cpu(); > > @@ -460,8 +456,6 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, > entry->eax &= supported; > entry->edx &= supported >> 32; > entry->flags |= KVM_CPUID_FLAG_SIGNIFCANT_INDEX; > - if (!supported) > - break; > > for (idx = 1, i = 1; idx < 64; ++idx) { > u64 mask = ((u64)1 << idx); > @@ -469,9 +463,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, > goto out; > > do_cpuid_1_ent(&entry[i], function, idx); > - if (idx == 1) > - entry[i].eax &= kvm_supported_word10_x86_features; > - else if (entry[i].eax == 0 || !(supported & mask)) > + if (entry[i].eax == 0 || !(supported & mask)) > continue; > entry[i].flags |= > KVM_CPUID_FLAG_SIGNIFCANT_INDEX; >