[PATCH v6 10/12] KVM: x86: Add XSAVE Support for Architectural LBR

[Yang Weijiang]

From: Like Xu <like.xu@xxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
 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 3815a32166a6..81d7a300fb6c 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7314,6 +7314,10 @@ 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()) {
+		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 2424d475a4d7..c09522c1f3ec 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);
-- 
2.21.1