KVM: SVM: merge update_cr0_intercept into svm_set_cr0

The logic of update_cr0_intercept is pointlessly complicated.
All svm_set_cr0 is compute the effective cr0 and compare it with
the guest value.

Inlining the function and simplifying the condition
clarifies what it is doing.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm/svm.c

@@ -1720,37 +1720,10 @@ static void svm_set_gdt(struct kvm_vcpu *vcpu, struct desc_ptr *dt)
 	vmcb_mark_dirty(svm->vmcb, VMCB_DT);
 }
 
-static void update_cr0_intercept(struct vcpu_svm *svm)
-{
-	ulong gcr0;
-	u64 *hcr0;
-
-	/*
-	 * SEV-ES guests must always keep the CR intercepts cleared. CR
-	 * tracking is done using the CR write traps.
-	 */
-	if (sev_es_guest(svm->vcpu.kvm))
-		return;
-
-	gcr0 = svm->vcpu.arch.cr0;
-	hcr0 = &svm->vmcb->save.cr0;
-	*hcr0 = (*hcr0 & ~SVM_CR0_SELECTIVE_MASK)
-		| (gcr0 & SVM_CR0_SELECTIVE_MASK);
-
-	vmcb_mark_dirty(svm->vmcb, VMCB_CR);
-
-	if (gcr0 == *hcr0) {
-		svm_clr_intercept(svm, INTERCEPT_CR0_READ);
-		svm_clr_intercept(svm, INTERCEPT_CR0_WRITE);
-	} else {
-		svm_set_intercept(svm, INTERCEPT_CR0_READ);
-		svm_set_intercept(svm, INTERCEPT_CR0_WRITE);
-	}
-}
-
 void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
+	u64 hcr0 = cr0;
 
 #ifdef CONFIG_X86_64
 	if (vcpu->arch.efer & EFER_LME && !vcpu->arch.guest_state_protected) {
@@ -1768,7 +1741,7 @@ void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 	vcpu->arch.cr0 = cr0;
 
 	if (!npt_enabled)
-		cr0 |= X86_CR0_PG | X86_CR0_WP;
+		hcr0 |= X86_CR0_PG | X86_CR0_WP;
 
 	/*
 	 * re-enable caching here because the QEMU bios
@@ -1776,10 +1749,27 @@ void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 	 * reboot
 	 */
 	if (kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_CD_NW_CLEARED))
-		cr0 &= ~(X86_CR0_CD | X86_CR0_NW);
-	svm->vmcb->save.cr0 = cr0;
+		hcr0 &= ~(X86_CR0_CD | X86_CR0_NW);
+
+	svm->vmcb->save.cr0 = hcr0;
 	vmcb_mark_dirty(svm->vmcb, VMCB_CR);
-	update_cr0_intercept(svm);
+
+	/*
+	 * SEV-ES guests must always keep the CR intercepts cleared. CR
+	 * tracking is done using the CR write traps.
+	 */
+	if (sev_es_guest(svm->vcpu.kvm))
+		return;
+
+	if (hcr0 == cr0) {
+		/* Selective CR0 write remains on.  */
+		svm_clr_intercept(svm, INTERCEPT_CR0_READ);
+		svm_clr_intercept(svm, INTERCEPT_CR0_WRITE);
+	} else {
+		svm_set_intercept(svm, INTERCEPT_CR0_READ);
+		svm_set_intercept(svm, INTERCEPT_CR0_WRITE);
+	}
+
 }
 
 static bool svm_is_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)