[PATCH v6 4/8] KVM: x86/pmu: Snapshot host IA32_PERF_CAPABILITIES in kvm_host

[Zide Chen <zide.chen@intel.com>]

From: Mingwei Zhang <mizhang@google.com>

Cache the unadulterated snapshot of perf_capabilities so that KVM can
compare guest vPMU capabilities against raw hardware capabilities.

For example, if the host supports PERF_METRICS but it is not configured
for the guest, KVM can use it to determine that RDPMC accesses must be
intercepted.

Signed-off-by: Mingwei Zhang <mizhang@google.com>
Signed-off-by: Zide Chen <zide.chen@intel.com>
---
v5: new patch.
---
 arch/x86/include/asm/kvm_host.h | 1 +
 arch/x86/kvm/vmx/vmx.c          | 8 ++------
 arch/x86/kvm/x86.c              | 4 ++++
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index dc9e4e8bfc07..80f638588bf7 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -347,6 +347,7 @@ struct kvm_host_values {
 	u64 xss;
 	u64 s_cet;
 	u64 arch_capabilities;
+	u64 perf_capabilities;
 };
 extern struct kvm_host_values kvm_host;
 
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index aded7039bd3e..b736b9ff965b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8050,14 +8050,10 @@ void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 static __init u64 vmx_get_perf_capabilities(void)
 {
 	u64 perf_cap = PERF_CAP_FW_WRITES;
-	u64 host_perf_cap = 0;
 
 	if (!enable_pmu)
 		return 0;
 
-	if (boot_cpu_has(X86_FEATURE_PDCM))
-		rdmsrq(MSR_IA32_PERF_CAPABILITIES, host_perf_cap);
-
 	if (!cpu_feature_enabled(X86_FEATURE_ARCH_LBR) &&
 	    !enable_mediated_pmu) {
 		x86_perf_get_lbr(&vmx_lbr_caps);
@@ -8070,11 +8066,11 @@ static __init u64 vmx_get_perf_capabilities(void)
 		if (!vmx_lbr_caps.has_callstack)
 			memset(&vmx_lbr_caps, 0, sizeof(vmx_lbr_caps));
 		else if (vmx_lbr_caps.nr)
-			perf_cap |= host_perf_cap & PERF_CAP_LBR_FMT;
+			perf_cap |= kvm_host.perf_capabilities & PERF_CAP_LBR_FMT;
 	}
 
 	if (vmx_pebs_supported()) {
-		perf_cap |= host_perf_cap & PERF_CAP_PEBS_MASK;
+		perf_cap |= kvm_host.perf_capabilities & PERF_CAP_PEBS_MASK;
 
 		/*
 		 * Disallow adaptive PEBS as it is functionally broken, can be
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8dbc0fa302a8..8e775855f9be 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7032,6 +7032,10 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
 	if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
 		rdmsrq(MSR_IA32_ARCH_CAPABILITIES, kvm_host.arch_capabilities);
 
+	if (boot_cpu_has(X86_FEATURE_PDCM))
+		rdmsrq_safe(MSR_IA32_PERF_CAPABILITIES,
+			    &kvm_host.perf_capabilities);
+
 	WARN_ON_ONCE(kvm_nr_uret_msrs);
 
 	r = ops->hardware_setup();
-- 
2.54.0