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From: Like Xu <like.xu@linux.intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	weijiang.yang@intel.com, wei.w.wang@intel.com,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [RESEND PATCH v4 10/10] KVM: x86: Add XSAVE Support for Architectural LBRs
Date: Mon, 10 May 2021 16:15:34 +0800	[thread overview]
Message-ID: <20210510081535.94184-11-like.xu@linux.intel.com> (raw)
In-Reply-To: <20210510081535.94184-1-like.xu@linux.intel.com>

On processors whose XSAVE feature set supports XSAVES and XRSTORS,
the availability of support for Architectural LBR configuration state save
and restore can be determined from CPUID.(EAX=0DH, ECX=1):EDX:ECX[bit 15].
The detailed leaf for Arch LBRs is enumerated in CPUID.(EAX=0DH, ECX=0FH).

XSAVES provides a faster means than RDMSR for guest to read all LBRs.
When guest IA32_XSS[bit 15] is set, the Arch LBRs state can be saved using
XSAVES and restored by XRSTORS with the appropriate RFBM.

If the KVM fails to pass-through the LBR msrs to the guest, the LBR msrs
will be reset to prevent the leakage of host records via XSAVES. In this
case, the guest results may be inaccurate as the legacy LBR.

Signed-off-by: Like Xu <like.xu@linux.intel.com>
---
 arch/x86/kvm/vmx/pmu_intel.c | 2 ++
 arch/x86/kvm/vmx/vmx.c       | 4 +++-
 arch/x86/kvm/x86.c           | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 9199d3974d57..7666292094ec 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -772,6 +772,8 @@ void vmx_passthrough_lbr_msrs(struct kvm_vcpu *vcpu)
 	return;
 
 warn:
+	if (kvm_cpu_cap_has(X86_FEATURE_ARCH_LBR))
+		wrmsrl(MSR_ARCH_LBR_DEPTH, lbr_desc->records.nr);
 	pr_warn_ratelimited("kvm: vcpu-%d: fail to passthrough LBR.\n",
 		vcpu->vcpu_id);
 }
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d080bf163565..9f610da71649 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7370,8 +7370,10 @@ static __init void vmx_set_cpu_caps(void)
 		kvm_cpu_cap_clear(X86_FEATURE_INVPCID);
 	if (vmx_pt_mode_is_host_guest())
 		kvm_cpu_cap_check_and_set(X86_FEATURE_INTEL_PT);
-	if (!cpu_has_vmx_arch_lbr())
+	if (!cpu_has_vmx_arch_lbr()) {
 		kvm_cpu_cap_clear(X86_FEATURE_ARCH_LBR);
+		supported_xss &= ~XFEATURE_MASK_LBR;
+	}
 
 	if (!enable_sgx) {
 		kvm_cpu_cap_clear(X86_FEATURE_SGX);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3a32bea2277e..7db24f287268 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -203,7 +203,7 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs;
 				| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
 				| XFEATURE_MASK_PKRU)
 
-#define KVM_SUPPORTED_XSS     0
+#define KVM_SUPPORTED_XSS     XFEATURE_MASK_LBR
 
 u64 __read_mostly host_efer;
 EXPORT_SYMBOL_GPL(host_efer);
-- 
2.31.1


  parent reply	other threads:[~2021-05-10  8:17 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-10  8:15 [RESEND PATCH v4 00/10] KVM: x86/pmu: Guest Architectural LBR Enabling Like Xu
2021-05-10  8:15 ` [RESEND PATCH v4 01/10] perf/x86/intel: Fix the comment about guest LBR support on KVM Like Xu
2021-05-10  8:15 ` [RESEND PATCH v4 02/10] perf/x86/lbr: Simplify the exposure check for the LBR_INFO registers Like Xu
2021-05-10  8:15 ` [RESEND PATCH v4 03/10] KVM: vmx/pmu: Add MSR_ARCH_LBR_DEPTH emulation for Arch LBR Like Xu
2021-06-23 18:03   ` Jim Mattson
2021-06-24  1:31     ` Yang Weijiang
2021-05-10  8:15 ` [RESEND PATCH v4 04/10] KVM: vmx/pmu: Add MSR_ARCH_LBR_CTL " Like Xu
2021-06-23 18:29   ` Jim Mattson
2021-06-24  1:35     ` Yang Weijiang
2021-05-10  8:15 ` [RESEND PATCH v4 05/10] KVM: vmx/pmu: Add Arch LBR emulation and its VMCS field Like Xu
2021-05-10  8:15 ` [RESEND PATCH v4 06/10] KVM: x86: Expose Architectural LBR CPUID leaf Like Xu
2021-05-10  8:15 ` [RESEND PATCH v4 07/10] KVM: x86: Refresh CPUID on writes to MSR_IA32_XSS Like Xu
2021-05-10  8:15 ` [RESEND PATCH v4 08/10] KVM: x86: Report XSS as an MSR to be saved if there are supported features Like Xu
2021-05-10  8:15 ` [RESEND PATCH v4 09/10] KVM: x86: Refine the matching and clearing logic for supported_xss Like Xu
2021-05-10  8:15 ` Like Xu [this message]
2021-05-10  8:15 ` [RESEND kvm-unit-tests PATCH v2] x86: Update guest LBR tests for Architectural LBR Like Xu
2021-06-22  9:01 ` [RESEND PATCH v4 00/10] KVM: x86/pmu: Guest Architectural LBR Enabling Yang Weijiang
2021-06-23 13:32   ` Like Xu

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