From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752616AbaLCMdj (ORCPT ); Wed, 3 Dec 2014 07:33:39 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33460 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751061AbaLCMdh (ORCPT ); Wed, 3 Dec 2014 07:33:37 -0500 Date: Wed, 3 Dec 2014 13:33:32 +0100 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: Wanpeng Li Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/3] kvm: x86: Enable Intel XSAVES for guest Message-ID: <20141203123331.GA26699@potion.brq.redhat.com> References: <1417519290-44063-1-git-send-email-wanpeng.li@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1417519290-44063-1-git-send-email-wanpeng.li@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2014-12-02 19:21+0800, Wanpeng Li: > Exporse intel xsaves feature to guest. 0xD.1:ebx ought to be non-zero with XSAVES, even if IA32_XSS is known to be 0, so we'll need to set it after Paolo's patch. > Signed-off-by: Wanpeng Li > --- > arch/x86/kvm/cpuid.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c > index a4f5ac4..0d919bc 100644 > --- a/arch/x86/kvm/cpuid.c > +++ b/arch/x86/kvm/cpuid.c > @@ -267,6 +267,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, > unsigned f_rdtscp = kvm_x86_ops->rdtscp_supported() ? F(RDTSCP) : 0; > unsigned f_invpcid = kvm_x86_ops->invpcid_supported() ? F(INVPCID) : 0; > unsigned f_mpx = kvm_x86_ops->mpx_supported() ? F(MPX) : 0; > + unsigned f_xsaves = kvm_x86_ops->xsaves_supported() ? F(XSAVES) : 0; > > /* cpuid 1.edx */ > const u32 kvm_supported_word0_x86_features = > @@ -322,7 +323,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function, > > /* cpuid 0xD.1.eax */ > const u32 kvm_supported_word10_x86_features = > - F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1); > + F(XSAVEOPT) | F(XSAVEC) | F(XGETBV1) | f_xsaves; > > /* all calls to cpuid_count() should be made on the same cpu */ > get_cpu(); > -- > 1.9.1 --- rant --- The documentation isn't clearly backward-compatible, it took me a while to understand why EBX Bits 31-00: The size in bytes of the XSAVE area containing all states enabled by XCRO | IA32_XSS. Is 0 on my old machine. Different section gives a better hint by mentioning XSAVES directly * EBX enumerates the size (in bytes) required by the XSAVES instruction for an XSAVE area containing all the state components corresponding to bits currently set in XCR0 | IA32_XSS.