[PATCH 1/6] KVM: vmx/pmu: Add VMCS field check before exposing LBR_FMT

[Like Xu]

If guest LBR_FMT is exposed on KVM, KVM needs to have guest state
field GUEST_IA32_DEBUGCTL and MSR_IA32_DEBUGCTLMSR vmx switch support.

Fixes: f93d622139de ("KVM: vmx/pmu: Expose LBR_FMT in the MSR_IA32_PERF_CAPABILITIES")
Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
---
 arch/x86/kvm/vmx/capabilities.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index 5829f4e9a7e0..f5f0586f4cd7 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -372,6 +372,12 @@ static inline bool vmx_pt_mode_is_host_guest(void)
 	return pt_mode == PT_MODE_HOST_GUEST;
 }
 
+static inline bool cpu_has_vmx_lbr(void)
+{
+	return (vmcs_config.vmexit_ctrl & VM_EXIT_SAVE_DEBUG_CONTROLS) &&
+		(vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_DEBUG_CONTROLS);
+}
+
 static inline u64 vmx_get_perf_capabilities(void)
 {
 	/*
@@ -383,7 +389,8 @@ static inline u64 vmx_get_perf_capabilities(void)
 	if (boot_cpu_has(X86_FEATURE_PDCM))
 		rdmsrl(MSR_IA32_PERF_CAPABILITIES, perf_cap);
 
-	perf_cap |= perf_cap & PMU_CAP_LBR_FMT;
+	if (cpu_has_vmx_lbr())
+		perf_cap |= perf_cap & PMU_CAP_LBR_FMT;
 
 	return perf_cap;
 }
-- 
2.21.3