[PATCH v2 2/4] KVM: vmx/pmu: Add MSR_ARCH_LBR_CTL emulation for Arch LBR

[Like Xu]

Arch LBRs are enabled by setting MSR_ARCH_LBR_CTL.LBREn to 1. On
processors that support Arch LBR, MSR_IA32_DEBUGCTLMSR[bit 0] has
no meaning. It can be written to 0 or 1, but reads will always return 0.

A new guest state field named "Guest IA32_LBR_CTL" has been added to
enhance guest LBR usage and the guest value of MSR_ARCH_LBR_CTL is
written to this field on all VM exits.

Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/vmx.h   |  2 ++
 arch/x86/kvm/vmx/pmu_intel.c | 14 ++++++++++++++
 arch/x86/kvm/vmx/vmx.c       |  7 +++++++
 3 files changed, 23 insertions(+)

diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index 1b387713eddd..c099c3d17612 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -247,6 +247,8 @@ enum vmcs_field {
 	GUEST_BNDCFGS_HIGH              = 0x00002813,
 	GUEST_IA32_RTIT_CTL		= 0x00002814,
 	GUEST_IA32_RTIT_CTL_HIGH	= 0x00002815,
+	GUEST_IA32_LBR_CTL		= 0x00002816,
+	GUEST_IA32_LBR_CTL_HIGH		= 0x00002817,
 	HOST_IA32_PAT			= 0x00002c00,
 	HOST_IA32_PAT_HIGH		= 0x00002c01,
 	HOST_IA32_EFER			= 0x00002c02,
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index b550c4a6ce33..a00d89c93eb7 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -19,6 +19,7 @@
 #include "pmu.h"
 
 #define MSR_PMC_FULL_WIDTH_BIT      (MSR_IA32_PMC0 - MSR_IA32_PERFCTR0)
+#define ARCH_LBR_CTL_MASK			0x7f000e
 
 static struct kvm_event_hw_type_mapping intel_arch_events[] = {
 	/* Index must match CPUID 0x0A.EBX bit vector */
@@ -221,6 +222,7 @@ static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
 		ret = pmu->version > 1;
 		break;
 	case MSR_ARCH_LBR_DEPTH:
+	case MSR_ARCH_LBR_CTL:
 		ret = guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR);
 		break;
 	default:
@@ -390,6 +392,9 @@ static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_ARCH_LBR_DEPTH:
 		msr_info->data = lbr_desc->records.nr;
 		return 0;
+	case MSR_ARCH_LBR_CTL:
+		msr_info->data = vmcs_read64(GUEST_IA32_LBR_CTL);
+		return 0;
 	default:
 		if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
 		    (pmc = get_gp_pmc(pmu, msr, MSR_IA32_PMC0))) {
@@ -458,6 +463,15 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		lbr_desc->arch_lbr_reset = true;
 		__set_bit(INTEL_PMC_IDX_FIXED_VLBR, pmu->pmc_in_use);
 		return 0;
+	case MSR_ARCH_LBR_CTL:
+		if (!(data & ARCH_LBR_CTL_MASK)) {
+			vmcs_write64(GUEST_IA32_LBR_CTL, data);
+			if (intel_pmu_lbr_is_enabled(vcpu) && !lbr_desc->event &&
+				(data & DEBUGCTLMSR_LBR))
+				intel_pmu_create_guest_lbr_event(vcpu);
+			return 0;
+		}
+		break;
 	default:
 		if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
 		    (pmc = get_gp_pmc(pmu, msr, MSR_IA32_PMC0))) {
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index beb5a912014d..edecf2961924 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2109,6 +2109,13 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 						VM_EXIT_SAVE_DEBUG_CONTROLS)
 			get_vmcs12(vcpu)->guest_ia32_debugctl = data;
 
+		/*
+		 * For Arch LBR, IA32_DEBUGCTL[bit 0] has no meaning.
+		 * It can be written to 0 or 1, but reads will always return 0.
+		 */
+		if (guest_cpuid_has(vcpu, X86_FEATURE_ARCH_LBR))
+			data &= ~DEBUGCTLMSR_LBR;
+
 		vmcs_write64(GUEST_IA32_DEBUGCTL, data);
 		if (intel_pmu_lbr_is_enabled(vcpu) && !to_vmx(vcpu)->lbr_desc.event &&
 		    (data & DEBUGCTLMSR_LBR))
-- 
2.29.2