KVM: x86: Fix reserved x2apic registers

x2APIC has no registers for DFR and ICR2 (see Intel SDM 10.12.1.2 "x2APIC
Register Address Space"). KVM needs to cause #GP on such accesses.

Fix it (DFR and ICR2 on read, ICR2 on write, DFR already handled on writes).
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/lapic.c

@@ -1883,6 +1883,9 @@ int kvm_x2apic_msr_write(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 	if (!irqchip_in_kernel(vcpu->kvm) || !apic_x2apic_mode(apic))
 		return 1;
 
+	if (reg == APIC_ICR2)
+		return 1;
+
 	/* if this is ICR write vector before command */
 	if (msr == 0x830)
 		apic_reg_write(apic, APIC_ICR2, (u32)(data >> 32));
@@ -1897,6 +1900,12 @@ int kvm_x2apic_msr_read(struct kvm_vcpu *vcpu, u32 msr, u64 *data)
 	if (!irqchip_in_kernel(vcpu->kvm) || !apic_x2apic_mode(apic))
 		return 1;
 
+	if (reg == APIC_DFR || reg == APIC_ICR2) {
+		apic_debug("KVM_APIC_READ: read x2apic reserved register %x\n",
+			   reg);
+		return 1;
+	}
+
 	if (apic_reg_read(apic, reg, 4, &low))
 		return 1;
 	if (msr == 0x830)