From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751311AbaLCBLR (ORCPT ); Tue, 2 Dec 2014 20:11:17 -0500 Received: from mga02.intel.com ([134.134.136.20]:41947 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751252AbaLCBLQ (ORCPT ); Tue, 2 Dec 2014 20:11:16 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,504,1413270000"; d="scan'208";a="617645155" Date: Wed, 3 Dec 2014 08:50:59 +0800 From: Wanpeng Li To: Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] kvm: x86: revert mask out xsaves Message-ID: <20141203005059.GA5084@kernel> Reply-To: Wanpeng Li References: <1417500894-7604-1-git-send-email-wanpeng.li@linux.intel.com> <547D7E6D.6090000@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <547D7E6D.6090000@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 02, 2014 at 09:55:09AM +0100, Paolo Bonzini wrote: > > >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). I will try to enable nested xsaves. Regards, Wanpeng Li > >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; >>