KVM: VMX: Smush x2APIC MSR bitmap adjustments into single function

Consolidate all of the dynamic MSR bitmap adjustments into
vmx_update_msr_bitmap_x2apic(), and rename the mode tracker to reflect
that it is x2APIC specific.  If KVM gains more cases of dynamic MSR
pass-through, odds are very good that those new cases will be better off
with their own logic, e.g. see Intel PT MSRs and MSR_IA32_SPEC_CTRL.

Attempting to handle all updates in a common helper did more harm than
good, as KVM ended up collecting a large number of useless "updates".
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210713163324.627647-42-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -3812,21 +3812,6 @@ void vmx_enable_intercept_for_msr(struct kvm_vcpu *vcpu, u32 msr, int type)
 		vmx_set_msr_bitmap_write(msr_bitmap, msr);
 }
 
-static u8 vmx_msr_bitmap_mode(struct kvm_vcpu *vcpu)
-{
-	u8 mode = 0;
-
-	if (cpu_has_secondary_exec_ctrls() &&
-	    (secondary_exec_controls_get(to_vmx(vcpu)) &
-	     SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE)) {
-		mode |= MSR_BITMAP_MODE_X2APIC;
-		if (enable_apicv && kvm_vcpu_apicv_active(vcpu))
-			mode |= MSR_BITMAP_MODE_X2APIC_APICV;
-	}
-
-	return mode;
-}
-
 static void vmx_reset_x2apic_msrs(struct kvm_vcpu *vcpu, u8 mode)
 {
 	unsigned long *msr_bitmap = to_vmx(vcpu)->vmcs01.msr_bitmap;
@@ -3844,11 +3829,29 @@ static void vmx_reset_x2apic_msrs(struct kvm_vcpu *vcpu, u8 mode)
 	}
 }
 
-static void vmx_update_msr_bitmap_x2apic(struct kvm_vcpu *vcpu, u8 mode)
+static void vmx_update_msr_bitmap_x2apic(struct kvm_vcpu *vcpu)
 {
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	u8 mode;
+
 	if (!cpu_has_vmx_msr_bitmap())
 		return;
 
+	if (cpu_has_secondary_exec_ctrls() &&
+	    (secondary_exec_controls_get(vmx) &
+	     SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE)) {
+		mode = MSR_BITMAP_MODE_X2APIC;
+		if (enable_apicv && kvm_vcpu_apicv_active(vcpu))
+			mode |= MSR_BITMAP_MODE_X2APIC_APICV;
+	} else {
+		mode = 0;
+	}
+
+	if (mode == vmx->x2apic_msr_bitmap_mode)
+		return;
+
+	vmx->x2apic_msr_bitmap_mode = mode;
+
 	vmx_reset_x2apic_msrs(vcpu, mode);
 
 	/*
@@ -3865,21 +3868,6 @@ static void vmx_update_msr_bitmap_x2apic(struct kvm_vcpu *vcpu, u8 mode)
 	}
 }
 
-static void vmx_update_msr_bitmap(struct kvm_vcpu *vcpu)
-{
-	struct vcpu_vmx *vmx = to_vmx(vcpu);
-	u8 mode = vmx_msr_bitmap_mode(vcpu);
-	u8 changed = mode ^ vmx->msr_bitmap_mode;
-
-	if (!changed)
-		return;
-
-	if (changed & (MSR_BITMAP_MODE_X2APIC | MSR_BITMAP_MODE_X2APIC_APICV))
-		vmx_update_msr_bitmap_x2apic(vcpu, mode);
-
-	vmx->msr_bitmap_mode = mode;
-}
-
 void pt_update_intercept_for_msr(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -4139,8 +4127,7 @@ static void vmx_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
 					SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY);
 	}
 
-	if (cpu_has_vmx_msr_bitmap())
-		vmx_update_msr_bitmap(vcpu);
+	vmx_update_msr_bitmap_x2apic(vcpu);
 }
 
 u32 vmx_exec_control(struct vcpu_vmx *vmx)
@@ -6190,7 +6177,7 @@ void vmx_set_virtual_apic_mode(struct kvm_vcpu *vcpu)
 	}
 	secondary_exec_controls_set(vmx, sec_exec_control);
 
-	vmx_update_msr_bitmap(vcpu);
+	vmx_update_msr_bitmap_x2apic(vcpu);
 }
 
 static void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu)

arch/x86/kvm/vmx/vmx.h

@@ -227,7 +227,7 @@ struct nested_vmx {
 struct vcpu_vmx {
 	struct kvm_vcpu       vcpu;
 	u8                    fail;
-	u8		      msr_bitmap_mode;
+	u8		      x2apic_msr_bitmap_mode;
 
 	/*
 	 * If true, host state has been stored in vmx->loaded_vmcs for