linux-kernel - [PATCH v12 11/16] KVM: x86: Add XSAVE Support for Architectural LBR

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Date:   Tue, 17 May 2022 11:40:55 -0400
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     pbonzini@...hat.com, jmattson@...gle.com, seanjc@...gle.com,
        like.xu.linux@...il.com, vkuznets@...hat.com,
        kan.liang@...ux.intel.com, wei.w.wang@...el.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Like Xu <like.xu@...ux.intel.com>,
        Yang Weijiang <weijiang.yang@...el.com>
Subject: [PATCH v12 11/16] KVM: x86: Add XSAVE Support for Architectural LBR

From: Like Xu <like.xu@...ux.intel.com>

On processors supporting XSAVES and XRSTORS, Architectural LBR XSAVE
support is enumerated from CPUID.(EAX=0DH, ECX=1):ECX[bit 15].
The detailed sub-leaf for Arch LBR is enumerated in CPUID.(0DH, 0FH).

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

Signed-off-by: Like Xu <like.xu@...ux.intel.com>
Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/kvm/vmx/vmx.c | 4 ++++
 arch/x86/kvm/x86.c     | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 7238628acb90..1b7194b9b6bc 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7546,6 +7546,10 @@ static __init void vmx_set_cpu_caps(void)
 		kvm_cpu_cap_check_and_set(X86_FEATURE_DS);
 		kvm_cpu_cap_check_and_set(X86_FEATURE_DTES64);
 	}
+	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 90b3129a2fbe..637ecd19c646 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -224,7 +224,7 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs;
 				| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
 				| XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE)
 
-#define KVM_SUPPORTED_XSS     0
+#define KVM_SUPPORTED_XSS     XFEATURE_MASK_LBR
 
 u64 __read_mostly host_efer;
 EXPORT_SYMBOL_GPL(host_efer);
-- 
2.27.0