KVM: x86: SVM: add module param to control LBR virtualization

This is useful for debug and also makes it consistent with
the rest of the SVM optional features.
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20210914154825.104886-9-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/svm.c

@@ -186,6 +186,10 @@ module_param(vls, int, 0444);
 static int vgif = true;
 module_param(vgif, int, 0444);
 
+/* enable/disable LBR virtualization */
+static int lbrv = true;
+module_param(lbrv, int, 0444);
+
 /*
  * enable / disable AVIC.  Because the defaults differ for APICv
  * support between VMX and SVM we cannot use module_param_named.
@@ -1059,6 +1063,13 @@ static __init int svm_hardware_setup(void)
 			pr_info("Virtual GIF supported\n");
 	}
 
+	if (lbrv) {
+		if (!boot_cpu_has(X86_FEATURE_LBRV))
+			lbrv = false;
+		else
+			pr_info("LBR virtualization supported\n");
+	}
+
 	svm_set_cpu_caps();
 
 	/*
@@ -2923,7 +2934,7 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 		svm->tsc_aux = data;
 		break;
 	case MSR_IA32_DEBUGCTLMSR:
-		if (!boot_cpu_has(X86_FEATURE_LBRV)) {
+		if (!lbrv) {
 			vcpu_unimpl(vcpu, "%s: MSR_IA32_DEBUGCTL 0x%llx, nop\n",
 				    __func__, data);
 			break;