From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 54BD3C43603 for ; Tue, 10 Dec 2019 21:27:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2EF6D205C9 for ; Tue, 10 Dec 2019 21:27:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728615AbfLJV1y (ORCPT ); Tue, 10 Dec 2019 16:27:54 -0500 Received: from mga07.intel.com ([134.134.136.100]:7237 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727656AbfLJV1t (ORCPT ); Tue, 10 Dec 2019 16:27:49 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 10 Dec 2019 13:27:48 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,301,1571727600"; d="scan'208";a="264657141" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.202]) by FMSMGA003.fm.intel.com with ESMTP; 10 Dec 2019 13:27:48 -0800 Date: Tue, 10 Dec 2019 13:27:48 -0800 From: Sean Christopherson To: Yang Weijiang Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, jmattson@google.com, yu.c.zhang@linux.intel.com, yu-cheng.yu@intel.com Subject: Re: [PATCH v8 6/7] KVM: X86: Load guest fpu state when accessing MSRs managed by XSAVES Message-ID: <20191210212748.GN15758@linux.intel.com> References: <20191101085222.27997-1-weijiang.yang@intel.com> <20191101085222.27997-7-weijiang.yang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191101085222.27997-7-weijiang.yang@intel.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 01, 2019 at 04:52:21PM +0800, Yang Weijiang wrote: > From: Sean Christopherson > > A handful of CET MSRs are not context switched through "traditional" > methods, e.g. VMCS or manual switching, but rather are passed through > to the guest and are saved and restored by XSAVES/XRSTORS, i.e. the > guest's FPU state. > > Load the guest's FPU state if userspace is accessing MSRs whose values > are managed by XSAVES so that the MSR helper, e.g. vmx_{get,set}_msr(), > can simply do {RD,WR}MSR to access the guest's value. > > Note that guest_cpuid_has() is not queried as host userspace is allowed > to access MSRs that have not been exposed to the guest, e.g. it might do > KVM_SET_MSRS prior to KVM_SET_CPUID2. > > Signed-off-by: Sean Christopherson > Co-developed-by: Yang Weijiang > Signed-off-by: Yang Weijiang > --- > arch/x86/kvm/x86.c | 21 ++++++++++++++++++++- > 1 file changed, 20 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 540490d5385f..6275a75d5802 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -104,6 +104,8 @@ static void enter_smm(struct kvm_vcpu *vcpu); > static void __kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags); > static void store_regs(struct kvm_vcpu *vcpu); > static int sync_regs(struct kvm_vcpu *vcpu); > +static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu); > +static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu); > > struct kvm_x86_ops *kvm_x86_ops __read_mostly; > EXPORT_SYMBOL_GPL(kvm_x86_ops); > @@ -3000,6 +3002,12 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) > } > EXPORT_SYMBOL_GPL(kvm_get_msr_common); > > +static bool is_xsaves_msr(u32 index) > +{ > + return index == MSR_IA32_U_CET || > + (index >= MSR_IA32_PL0_SSP && index <= MSR_IA32_PL3_SSP); > +} > + > /* > * Read or write a bunch of msrs. All parameters are kernel addresses. > * > @@ -3010,11 +3018,22 @@ static int __msr_io(struct kvm_vcpu *vcpu, struct kvm_msrs *msrs, > int (*do_msr)(struct kvm_vcpu *vcpu, > unsigned index, u64 *data)) > { > + bool fpu_loaded = false; > int i; > + const u64 cet_bits = XFEATURE_MASK_CET_USER | XFEATURE_MASK_CET_KERNEL; > + bool cet_xss = kvm_supported_xss() & cet_bits; > > - for (i = 0; i < msrs->nmsrs; ++i) > + for (i = 0; i < msrs->nmsrs; ++i) { > + if (!fpu_loaded && cet_xss && > + is_xsaves_msr(entries[i].index)) { > + kvm_load_guest_fpu(vcpu); This needs to also check for a non-NULL @vcpu. KVM_GET_MSR can be called on the VM to invoke do_get_msr_feature(). > + fpu_loaded = true; > + } > if (do_msr(vcpu, entries[i].index, &entries[i].data)) > break; > + } > + if (fpu_loaded) > + kvm_put_guest_fpu(vcpu); > > return i; > } > -- > 2.17.2 >