KVM: SVM: Introduce svm_recalc_lbr_msr_intercepts()

Introduce a helper updating the intercepts for LBR MSRs, similar to the
one introduced upstream by commit 160f143 ("KVM: SVM: Manually
recalc all MSR intercepts on userspace MSR filter change"). The main
difference is that this version uses set_msr_interception(), which has
inverted polarity compared to svm_set_intercept_for_msr().

This is intended to simplify incoming backports. No functional changes
intended.

Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: yosrym93

arch/x86/kvm/svm/svm.c

@@ -995,18 +995,31 @@ void svm_copy_lbrs(struct vmcb *to_vmcb, struct vmcb *from_vmcb)
 	vmcb_mark_dirty(to_vmcb, VMCB_LBR);
 }
 
-void svm_enable_lbrv(struct kvm_vcpu *vcpu)
+static void svm_recalc_lbr_msr_intercepts(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
+	bool intercept = !(svm->vmcb->control.virt_ext & LBR_CTL_ENABLE_MASK);
 
-	svm->vmcb->control.virt_ext |= LBR_CTL_ENABLE_MASK;
-	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTBRANCHFROMIP, 1, 1);
-	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTBRANCHTOIP, 1, 1);
-	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTINTFROMIP, 1, 1);
-	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTINTTOIP, 1, 1);
+	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTBRANCHFROMIP,
+			     !intercept, !intercept);
+	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTBRANCHTOIP,
+			     !intercept, !intercept);
+	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTINTFROMIP,
+			     !intercept, !intercept);
+	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTINTTOIP,
+			     !intercept, !intercept);
 
 	if (sev_es_guest(vcpu->kvm))
-		set_msr_interception(vcpu, svm->msrpm, MSR_IA32_DEBUGCTLMSR, 1, 1);
+		set_msr_interception(vcpu, svm->msrpm, MSR_IA32_DEBUGCTLMSR,
+				     !intercept, !intercept);
+}
+
+void svm_enable_lbrv(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	svm->vmcb->control.virt_ext |= LBR_CTL_ENABLE_MASK;
+	svm_recalc_lbr_msr_intercepts(vcpu);
 
 	/* Move the LBR msrs to the vmcb02 so that the guest can see them. */
 	if (is_guest_mode(vcpu))
@@ -1020,10 +1033,7 @@ static void svm_disable_lbrv(struct kvm_vcpu *vcpu)
 	KVM_BUG_ON(sev_es_guest(vcpu->kvm), vcpu->kvm);
 
 	svm->vmcb->control.virt_ext &= ~LBR_CTL_ENABLE_MASK;
-	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTBRANCHFROMIP, 0, 0);
-	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTBRANCHTOIP, 0, 0);
-	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTINTFROMIP, 0, 0);
-	set_msr_interception(vcpu, svm->msrpm, MSR_IA32_LASTINTTOIP, 0, 0);
+	svm_recalc_lbr_msr_intercepts(vcpu);
 
 	/*
 	 * Move the LBR msrs back to the vmcb01 to avoid copying them