KVM: SVM: Fix potential wrong physical id in avic_handle_ldr_update

Guest physical APIC ID may not equal to vcpu->vcpu_id in some case.
We may set the wrong physical id in avic_handle_ldr_update as we
always use vcpu->vcpu_id. Get physical APIC ID from vAPIC page
instead.
Export and use kvm_xapic_id here and in avic_handle_apic_id_update
as suggested by Vitaly.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/lapic.c

@@ -111,11 +111,6 @@ static inline int apic_enabled(struct kvm_lapic *apic)
 	(LVT_MASK | APIC_MODE_MASK | APIC_INPUT_POLARITY | \
 	 APIC_LVT_REMOTE_IRR | APIC_LVT_LEVEL_TRIGGER)
 
-static inline u8 kvm_xapic_id(struct kvm_lapic *apic)
-{
-	return kvm_lapic_get_reg(apic, APIC_ID) >> 24;
-}
-
 static inline u32 kvm_x2apic_id(struct kvm_lapic *apic)
 {
 	return apic->vcpu->vcpu_id;

arch/x86/kvm/lapic.h

@@ -242,4 +242,9 @@ static inline enum lapic_mode kvm_apic_mode(u64 apic_base)
 	return apic_base & (MSR_IA32_APICBASE_ENABLE | X2APIC_ENABLE);
 }
 
+static inline u8 kvm_xapic_id(struct kvm_lapic *apic)
+{
+	return kvm_lapic_get_reg(apic, APIC_ID) >> 24;
+}
+
 #endif

arch/x86/kvm/svm.c

@@ -4591,6 +4591,7 @@ static int avic_handle_ldr_update(struct kvm_vcpu *vcpu)
 	int ret = 0;
 	struct vcpu_svm *svm = to_svm(vcpu);
 	u32 ldr = kvm_lapic_get_reg(vcpu->arch.apic, APIC_LDR);
+	u32 id = kvm_xapic_id(vcpu->arch.apic);
 
 	if (ldr == svm->ldr_reg)
 		return 0;
@@ -4598,7 +4599,7 @@ static int avic_handle_ldr_update(struct kvm_vcpu *vcpu)
 	avic_invalidate_logical_id_entry(vcpu);
 
 	if (ldr)
-		ret = avic_ldr_write(vcpu, vcpu->vcpu_id, ldr);
+		ret = avic_ldr_write(vcpu, id, ldr);
 
 	if (!ret)
 		svm->ldr_reg = ldr;
@@ -4610,8 +4611,7 @@ static int avic_handle_apic_id_update(struct kvm_vcpu *vcpu)
 {
 	u64 *old, *new;
 	struct vcpu_svm *svm = to_svm(vcpu);
-	u32 apic_id_reg = kvm_lapic_get_reg(vcpu->arch.apic, APIC_ID);
-	u32 id = (apic_id_reg >> 24) & 0xff;
+	u32 id = kvm_xapic_id(vcpu->arch.apic);
 
 	if (vcpu->vcpu_id == id)
 		return 0;