[PATCH v13 09/10] KVM: vmx/pmu: Expose LBR_FMT in the MSR_IA32_PERF_CAPABILITIES

[Like Xu]

Userspace could enable guest LBR feature when the exactly supported
LBR format value is initialized to the MSR_IA32_PERF_CAPABILITIES
and the LBR is also compatible with vPMU version and host cpu model.

Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
---
 arch/x86/kvm/vmx/capabilities.h |  9 ++++++++-
 arch/x86/kvm/vmx/vmx.c          | 10 ++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index f17ab6cf152e..5829f4e9a7e0 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -378,7 +378,14 @@ static inline u64 vmx_get_perf_capabilities(void)
 	 * Since counters are virtualized, KVM would support full
 	 * width counting unconditionally, even if the host lacks it.
 	 */
-	return PMU_CAP_FW_WRITES;
+	u64 perf_cap = PMU_CAP_FW_WRITES;
+
+	if (boot_cpu_has(X86_FEATURE_PDCM))
+		rdmsrl(MSR_IA32_PERF_CAPABILITIES, perf_cap);
+
+	perf_cap |= perf_cap & PMU_CAP_LBR_FMT;
+
+	return perf_cap;
 }
 
 static inline u64 vmx_supported_debugctl(void)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b72fbbef56fa..6d8b1d98ae1d 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2251,6 +2251,16 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		if ((data >> 32) != 0)
 			return 1;
 		goto find_shared_msr;
+	case MSR_IA32_PERF_CAPABILITIES:
+		if (data & PMU_CAP_LBR_FMT) {
+			if ((data & PMU_CAP_LBR_FMT) !=
+			    (vmx_get_perf_capabilities() & PMU_CAP_LBR_FMT))
+				return 1;
+			if (!intel_pmu_lbr_is_compatible(vcpu))
+				return 1;
+		}
+		ret = kvm_set_msr_common(vcpu, msr_info);
+		break;
 
 	default:
 	find_shared_msr:
-- 
2.21.3