[RFC v1 9/9] KVM: x86: Expose PEBS feature to guest

[Luwei Kang]

Expose PEBS feature to guest by IA32_MISC_ENABLE[bit12].
IA32_MISC_ENABLE[bit12] is Processor Event Based Sampling (PEBS)
Unavailable (RO) flag:
1 = PEBS is not supported; 0 = PEBS is supported.

Signed-off-by: Luwei Kang <luwei.kang@xxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/svm.c              |  6 ++++++
 arch/x86/kvm/vmx/vmx.c          |  1 +
 arch/x86/kvm/x86.c              | 22 +++++++++++++++++-----
 4 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 94af338..f6a5630 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1130,6 +1130,7 @@ struct kvm_x86_ops {
 	bool (*xsaves_supported)(void);
 	bool (*umip_emulated)(void);
 	bool (*pt_supported)(void);
+	bool (*pebs_supported)(void);
 	bool (*pdcm_supported)(void);
 
 	int (*check_nested_events)(struct kvm_vcpu *vcpu, bool external_intr);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 8ae6716..2b271fc 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -6005,6 +6005,11 @@ static bool svm_pt_supported(void)
 	return false;
 }
 
+static bool svm_pebs_supported(void)
+{
+	return false;
+}
+
 static bool svm_pdcm_supported(void)
 {
 	return false;
@@ -7298,6 +7303,7 @@ static bool svm_need_emulation_on_page_fault(struct kvm_vcpu *vcpu)
 	.xsaves_supported = svm_xsaves_supported,
 	.umip_emulated = svm_umip_emulated,
 	.pt_supported = svm_pt_supported,
+	.pebs_supported = svm_pebs_supported,
 	.pdcm_supported = svm_pdcm_supported,
 
 	.set_supported_cpuid = svm_set_supported_cpuid,
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 71e3d42..d85f19b 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7782,6 +7782,7 @@ static __exit void hardware_unsetup(void)
 	.xsaves_supported = vmx_xsaves_supported,
 	.umip_emulated = vmx_umip_emulated,
 	.pt_supported = vmx_pt_supported,
+	.pebs_supported = vmx_pebs_supported,
 	.pdcm_supported = vmx_pdcm_supported,
 
 	.request_immediate_exit = vmx_request_immediate_exit,
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 290c3c3..8ad501d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2483,6 +2483,7 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
 int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
 	bool pr = false;
+	bool update_cpuid = false;
 	u32 msr = msr_info->index;
 	u64 data = msr_info->data;
 
@@ -2563,11 +2564,17 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		    ((vcpu->arch.ia32_misc_enable_msr ^ data) & MSR_IA32_MISC_ENABLE_MWAIT)) {
 			if (!guest_cpuid_has(vcpu, X86_FEATURE_XMM3))
 				return 1;
-			vcpu->arch.ia32_misc_enable_msr = data;
-			kvm_update_cpuid(vcpu);
-		} else {
-			vcpu->arch.ia32_misc_enable_msr = data;
+			update_cpuid = true;
 		}
+
+		if (kvm_x86_ops->pebs_supported())
+			data &=  ~MSR_IA32_MISC_ENABLE_PEBS;
+		else
+			data |= MSR_IA32_MISC_ENABLE_PEBS;
+
+		vcpu->arch.ia32_misc_enable_msr = data;
+		if (update_cpuid)
+			kvm_update_cpuid(vcpu);
 		break;
 	case MSR_IA32_SMBASE:
 		if (!msr_info->host_initiated)
@@ -2875,7 +2882,12 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		msr_info->data = (u64)vcpu->arch.ia32_tsc_adjust_msr;
 		break;
 	case MSR_IA32_MISC_ENABLE:
-		msr_info->data = vcpu->arch.ia32_misc_enable_msr;
+		if (kvm_x86_ops->pebs_supported())
+			msr_info->data = (vcpu->arch.ia32_misc_enable_msr &
+						~MSR_IA32_MISC_ENABLE_PEBS);
+		else
+			msr_info->data = (vcpu->arch.ia32_misc_enable_msr |
+						MSR_IA32_MISC_ENABLE_PEBS);
 		break;
 	case MSR_IA32_SMBASE:
 		if (!msr_info->host_initiated)
-- 
1.8.3.1