[PATCH v2 4/8] KVM/x86: expose MSR_IA32_PERF_CAPABILITIES to the guest

[Wei Wang]

Bits [0, 5] of MSR_IA32_PERF_CAPABILITIES tell about the format of
the addresses stored in the LBR stack. Expose those bits to the guest
when the guest lbr feature is enabled.

Signed-off-by: Like Xu <like...@intel.com>
Signed-off-by: Wei Wang <wei.w.w...@intel.com>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Cc: Andi Kleen <a...@linux.intel.com>
---
 arch/x86/include/asm/perf_event.h | 2 ++
 arch/x86/kvm/cpuid.c              | 2 +-
 arch/x86/kvm/vmx.c                | 7 +++++++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/perf_event.h 
b/arch/x86/include/asm/perf_event.h
index f40e80a..161165f 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -79,6 +79,8 @@
 #define ARCH_PERFMON_BRANCH_MISSES_RETIRED             6
 #define ARCH_PERFMON_EVENTS_COUNT                      7
 
+#define PERF_CAP_MASK_LBR_FMT                          0x3f
+
 /*
  * Intel "Architectural Performance Monitoring" CPUID
  * detection/enumeration details:
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 7bcfa61..3b8a57b 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -365,7 +365,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 
*entry, u32 function,
                F(XMM3) | F(PCLMULQDQ) | 0 /* DTES64, MONITOR */ |
                0 /* DS-CPL, VMX, SMX, EST */ |
                0 /* TM2 */ | F(SSSE3) | 0 /* CNXT-ID */ | 0 /* Reserved */ |
-               F(FMA) | F(CX16) | 0 /* xTPR Update, PDCM */ |
+               F(FMA) | F(CX16) | 0 /* xTPR Update*/ | F(PDCM) |
                F(PCID) | 0 /* Reserved, DCA */ | F(XMM4_1) |
                F(XMM4_2) | F(X2APIC) | F(MOVBE) | F(POPCNT) |
                0 /* Reserved*/ | F(AES) | F(XSAVE) | 0 /* OSXSAVE */ | F(AVX) |
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 7a62c1c..d5eba8e 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4134,6 +4134,13 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct 
msr_data *msr_info)
                    !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
                        return 1;
                /* Otherwise falls through */
+       case MSR_IA32_PERF_CAPABILITIES:
+               if (!boot_cpu_has(X86_FEATURE_PDCM))
+                       return 1;
+               msr_info->data = native_read_msr(MSR_IA32_PERF_CAPABILITIES);
+               if (vcpu->kvm->arch.guest_lbr)
+                       msr_info->data &= PERF_CAP_MASK_LBR_FMT;
+               break;
        default:
                msr = find_msr_entry(vmx, msr_info->index);
                if (msr) {
-- 
2.7.4