3 files changed, 135 insertions, 3 deletions

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index dbaa175a3c2e..c7dbaaccbcaa 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -190,6 +190,24 @@ bool intel_pmu_lbr_is_enabled(struct kvm_vcpu *vcpu)
 	return lbr->nr && (vcpu_get_perf_capabilities(vcpu) & PMU_CAP_LBR_FMT);
 }
 
+static bool intel_pmu_is_valid_lbr_msr(struct kvm_vcpu *vcpu, u32 index)
+{
+	struct x86_pmu_lbr *records = vcpu_to_lbr_records(vcpu);
+	bool ret = false;
+
+	if (!intel_pmu_lbr_is_enabled(vcpu))
+		return ret;
+
+	ret = (index == MSR_LBR_SELECT) || (index == MSR_LBR_TOS) ||
+		(index >= records->from && index < records->from + records->nr) ||
+		(index >= records->to && index < records->to + records->nr);
+
+	if (!ret && records->info)
+		ret = (index >= records->info && index < records->info + records->nr);
+
+	return ret;
+}
+
 static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
@@ -205,7 +223,8 @@ static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
 	default:
 		ret = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0) ||
 			get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0) ||
-			get_fixed_pmc(pmu, msr) || get_fw_gp_pmc(pmu, msr);
+			get_fixed_pmc(pmu, msr) || get_fw_gp_pmc(pmu, msr) ||
+			intel_pmu_is_valid_lbr_msr(vcpu, msr);
 		break;
 	}
 
@@ -284,6 +303,46 @@ int intel_pmu_create_guest_lbr_event(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
+/*
+ * It's safe to access LBR msrs from guest when they have not
+ * been passthrough since the host would help restore or reset
+ * the LBR msrs records when the guest LBR event is scheduled in.
+ */
+static bool intel_pmu_handle_lbr_msrs_access(struct kvm_vcpu *vcpu,
+				     struct msr_data *msr_info, bool read)
+{
+	struct lbr_desc *lbr_desc = vcpu_to_lbr_desc(vcpu);
+	u32 index = msr_info->index;
+
+	if (!intel_pmu_is_valid_lbr_msr(vcpu, index))
+		return false;
+
+	if (!lbr_desc->event && !intel_pmu_create_guest_lbr_event(vcpu))
+		goto dummy;
+
+	/*
+	 * Disable irq to ensure the LBR feature doesn't get reclaimed by the
+	 * host at the time the value is read from the msr, and this avoids the
+	 * host LBR value to be leaked to the guest. If LBR has been reclaimed,
+	 * return 0 on guest reads.
+	 */
+	local_irq_disable();
+	if (lbr_desc->event->state == PERF_EVENT_STATE_ACTIVE) {
+		if (read)
+			rdmsrl(index, msr_info->data);
+		else
+			wrmsrl(index, msr_info->data);
+		local_irq_enable();
+		return true;
+	}
+	local_irq_enable();
+
+dummy:
+	if (read)
+		msr_info->data = 0;
+	return true;
+}
+
 static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
@@ -318,7 +377,8 @@ static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		} else if ((pmc = get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0))) {
 			msr_info->data = pmc->eventsel;
 			return 0;
-		}
+		} else if (intel_pmu_handle_lbr_msrs_access(vcpu, msr_info, true))
+			return 0;
 	}
 
 	return 1;
@@ -389,7 +449,8 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 				reprogram_gp_counter(pmc, data);
 				return 0;
 			}
-		}
+		} else if (intel_pmu_handle_lbr_msrs_access(vcpu, msr_info, false))
+			return 0;
 	}
 
 	return 1;
@@ -524,6 +585,66 @@ static void intel_pmu_reset(struct kvm_vcpu *vcpu)
 	intel_pmu_release_guest_lbr_event(vcpu);
 }
 
+static void vmx_update_intercept_for_lbr_msrs(struct kvm_vcpu *vcpu, bool set)
+{
+	struct x86_pmu_lbr *lbr = vcpu_to_lbr_records(vcpu);
+	int i;
+
+	for (i = 0; i < lbr->nr; i++) {
+		vmx_set_intercept_for_msr(vcpu, lbr->from + i, MSR_TYPE_RW, set);
+		vmx_set_intercept_for_msr(vcpu, lbr->to + i, MSR_TYPE_RW, set);
+		if (lbr->info)
+			vmx_set_intercept_for_msr(vcpu, lbr->info + i, MSR_TYPE_RW, set);
+	}
+
+	vmx_set_intercept_for_msr(vcpu, MSR_LBR_SELECT, MSR_TYPE_RW, set);
+	vmx_set_intercept_for_msr(vcpu, MSR_LBR_TOS, MSR_TYPE_RW, set);
+}
+
+static inline void vmx_disable_lbr_msrs_passthrough(struct kvm_vcpu *vcpu)
+{
+	vmx_update_intercept_for_lbr_msrs(vcpu, true);
+}
+
+static inline void vmx_enable_lbr_msrs_passthrough(struct kvm_vcpu *vcpu)
+{
+	vmx_update_intercept_for_lbr_msrs(vcpu, false);
+}
+
+/*
+ * Higher priority host perf events (e.g. cpu pinned) could reclaim the
+ * pmu resources (e.g. LBR) that were assigned to the guest. This is
+ * usually done via ipi calls (more details in perf_install_in_context).
+ *
+ * Before entering the non-root mode (with irq disabled here), double
+ * confirm that the pmu features enabled to the guest are not reclaimed
+ * by higher priority host events. Otherwise, disallow vcpu's access to
+ * the reclaimed features.
+ */
+void vmx_passthrough_lbr_msrs(struct kvm_vcpu *vcpu)
+{
+	struct lbr_desc *lbr_desc = vcpu_to_lbr_desc(vcpu);
+
+	if (!lbr_desc->event) {
+		vmx_disable_lbr_msrs_passthrough(vcpu);
+		if (vmcs_read64(GUEST_IA32_DEBUGCTL) & DEBUGCTLMSR_LBR)
+			goto warn;
+		return;
+	}
+
+	if (lbr_desc->event->state < PERF_EVENT_STATE_ACTIVE) {
+		vmx_disable_lbr_msrs_passthrough(vcpu);
+		goto warn;
+	} else
+		vmx_enable_lbr_msrs_passthrough(vcpu);
+
+	return;
+
+warn:
+	pr_warn_ratelimited("kvm: vcpu-%d: fail to passthrough LBR.\n",
+		vcpu->vcpu_id);
+}
+
 struct kvm_pmu_ops intel_pmu_ops = {
 	.find_arch_event = intel_find_arch_event,
 	.find_fixed_event = intel_find_fixed_event,
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 194458077dcb..e2f8c3c68f02 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -658,6 +658,14 @@ static bool is_valid_passthrough_msr(u32 msr)
 	case MSR_IA32_RTIT_CR3_MATCH:
 	case MSR_IA32_RTIT_ADDR0_A ... MSR_IA32_RTIT_ADDR3_B:
 		/* PT MSRs. These are handled in pt_update_intercept_for_msr() */
+	case MSR_LBR_SELECT:
+	case MSR_LBR_TOS:
+	case MSR_LBR_INFO_0 ... MSR_LBR_INFO_0 + 31:
+	case MSR_LBR_NHM_FROM ... MSR_LBR_NHM_FROM + 31:
+	case MSR_LBR_NHM_TO ... MSR_LBR_NHM_TO + 31:
+	case MSR_LBR_CORE_FROM ... MSR_LBR_CORE_FROM + 8:
+	case MSR_LBR_CORE_TO ... MSR_LBR_CORE_TO + 8:
+		/* LBR MSRs. These are handled in vmx_update_intercept_for_lbr_msrs() */
 		return true;
 	}
 
@@ -6769,6 +6777,8 @@ reenter_guest:
 	pt_guest_enter(vmx);
 
 	atomic_switch_perf_msrs(vmx);
+	if (intel_pmu_lbr_is_enabled(vcpu))
+		vmx_passthrough_lbr_msrs(vcpu);
 
 	if (enable_preemption_timer)
 		vmx_update_hv_timer(vcpu);
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 8f33832db044..41bf9adfcb79 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -100,6 +100,7 @@ bool intel_pmu_lbr_is_compatible(struct kvm_vcpu *vcpu);
 bool intel_pmu_lbr_is_enabled(struct kvm_vcpu *vcpu);
 
 int intel_pmu_create_guest_lbr_event(struct kvm_vcpu *vcpu);
+void vmx_passthrough_lbr_msrs(struct kvm_vcpu *vcpu);
 
 struct lbr_desc {
 	/* Basic info about guest LBR records. */