From patchwork Fri Nov 1 08:52:21 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Yang, Weijiang" X-Patchwork-Id: 11222767 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 055951747 for ; Fri, 1 Nov 2019 08:50:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DDA1521A4A for ; Fri, 1 Nov 2019 08:50:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727561AbfKAIuE (ORCPT ); Fri, 1 Nov 2019 04:50:04 -0400 Received: from mga14.intel.com ([192.55.52.115]:34433 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727507AbfKAIuB (ORCPT ); Fri, 1 Nov 2019 04:50:01 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 01 Nov 2019 01:50:00 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,254,1569308400"; d="scan'208";a="194606626" Received: from unknown (HELO local-michael-cet-test.sh.intel.com) ([10.239.159.128]) by orsmga008.jf.intel.com with ESMTP; 01 Nov 2019 01:49:59 -0700 From: Yang Weijiang To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, pbonzini@redhat.com, sean.j.christopherson@intel.com Cc: jmattson@google.com, yu.c.zhang@linux.intel.com, yu-cheng.yu@intel.com, Yang Weijiang Subject: [PATCH v8 6/7] KVM: X86: Load guest fpu state when accessing MSRs managed by XSAVES Date: Fri, 1 Nov 2019 16:52:21 +0800 Message-Id: <20191101085222.27997-7-weijiang.yang@intel.com> X-Mailer: git-send-email 2.17.2 In-Reply-To: <20191101085222.27997-1-weijiang.yang@intel.com> References: <20191101085222.27997-1-weijiang.yang@intel.com> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 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); + fpu_loaded = true; + } if (do_msr(vcpu, entries[i].index, &entries[i].data)) break; + } + if (fpu_loaded) + kvm_put_guest_fpu(vcpu); return i; }