[PATCH 13/15] KVM: x86/pmu: Ignore AnyThread bit if CPUID.0AH:EDX[15] is not set

[Zide Chen]

Intel PerfMon v5 introduces the ANYTHREAD_DEPRECATION capability
(CPUID.0AH:EDX[15]) to indicate that AnyThread counting is deprecated
and that writes to the AnyThread bit in IA32_PERFEVTSELx are ignored.

When ANYTHREAD_DEPRECATION is present in the guest CPUID, emulate the
architectural behavior and silently ignore writes to the AnyThread bit
instead of injecting #GP.

Continue to inject #GP when ANYTHREAD_DEPRECATION is not present in the
guest CPUID, e.g. for PerfMon v3/v4 guests or when the capability is
not configured for a PerfMon v5+ guest.

Signed-off-by: Zide Chen <zide.chen@xxxxxxxxx>
---
 arch/x86/kvm/vmx/pmu_intel.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 3f41e4916986..2c2a54ac55ad 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -508,6 +508,11 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			if (data & eventsel_rsvd)
 				return 1;
 
+			/*
+			 * On PerfMon v5+, KVM may allow writes to the AnyThread
+			 * bit and silently discard them.
+			 */
+			data &= ~ARCH_PERFMON_EVENTSEL_ANY;
 			if (data != pmc->eventsel) {
 				pmc->eventsel = data;
 				pmc->eventsel_hw = data;
@@ -627,6 +632,9 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 	pmu->all_valid_pmc_mask64 = (BIT_ULL(nr_gp_counters) - 1) &
 				    kvm_pmu_cap.cntr_mask64;
 
+	if (pmu->version >= 5 && edx.split.anythread_deprecated)
+		pmu->eventsel_rsvd &= ~ARCH_PERFMON_EVENTSEL_ANY;
+
 	entry = kvm_find_cpuid_entry_index(vcpu, 7, 0);
 	if (entry &&
 	    (boot_cpu_has(X86_FEATURE_HLE) || boot_cpu_has(X86_FEATURE_RTM)) &&
-- 
2.54.0