[RFC PATCH 09/13] KVM: SVM: Introduce helper function avic_get_apic_id

[Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>]

This function returns the currently programmed guest physical
APIC ID of a vCPU in both xAPIC and x2APIC modes.
In case of invalid APIC ID based on the current mode,
the function returns X2APIC_BROADCAST.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@xxxxxxx>
---
 arch/x86/kvm/svm/avic.c | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 55b3b703b93b..3543b7a4514a 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -450,16 +450,35 @@ static void avic_invalidate_logical_id_entry(struct kvm_vcpu *vcpu)
 		clear_bit(AVIC_LOGICAL_ID_ENTRY_VALID_BIT, (unsigned long *)entry);
 }
 
+static inline u32 avic_get_apic_id(struct kvm_vcpu *vcpu)
+{
+	u32 apic_id = kvm_lapic_get_reg(vcpu->arch.apic, APIC_ID);
+
+	if (!apic_x2apic_mode(vcpu->arch.apic)) {
+		/*
+		 * In case of xAPIC, we do not support
+		 * APIC ID larger than 254.
+		 */
+		if (vcpu->vcpu_id >= APIC_BROADCAST)
+			return X2APIC_BROADCAST;
+		return apic_id >> 24;
+	} else
+		return apic_id;
+}
+
 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);
+	u32 id = avic_get_apic_id(vcpu);
 
 	if (ldr == svm->ldr_reg)
 		return 0;
 
+	if (id == X2APIC_BROADCAST)
+		return -EINVAL;
+
 	avic_invalidate_logical_id_entry(vcpu);
 
 	if (ldr)
@@ -475,7 +494,10 @@ static int avic_handle_apic_id_update(struct kvm_vcpu *vcpu)
 {
 	u64 *old, *new;
 	struct vcpu_svm *svm = to_svm(vcpu);
-	u32 id = kvm_xapic_id(vcpu->arch.apic);
+	u32 id = avic_get_apic_id(vcpu);
+
+	if (id == X2APIC_BROADCAST)
+		return 1;
 
 	if (vcpu->vcpu_id == id)
 		return 0;
@@ -497,7 +519,8 @@ static int avic_handle_apic_id_update(struct kvm_vcpu *vcpu)
 	 * APIC ID table entry if already setup the LDR.
 	 */
 	if (svm->ldr_reg)
-		avic_handle_ldr_update(vcpu);
+		if (avic_handle_ldr_update(vcpu))
+			return 1;
 
 	return 0;
 }
-- 
2.25.1