KVM: x86: use hardware-compatible format for APIC ID register

We currently always shift APIC ID as if APIC was in xAPIC mode.
x2APIC mode wants to use more bits and storing a hardware-compabible
value is the the sanest option.

KVM API to set the lapic expects that bottom 8 bits of APIC ID are in
top 8 bits of APIC_ID register, so the register needs to be shifted in
x2APIC mode.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/lapic.c

@@ -227,7 +227,7 @@ static inline void apic_set_spiv(struct kvm_lapic *apic, u32 val)
 	}
 }
 
-static inline void kvm_apic_set_id(struct kvm_lapic *apic, u8 id)
+static inline void kvm_apic_set_xapic_id(struct kvm_lapic *apic, u8 id)
 {
 	kvm_lapic_set_reg(apic, APIC_ID, id << 24);
 	recalculate_apic_map(apic->vcpu->kvm);
@@ -239,11 +239,11 @@ static inline void kvm_apic_set_ldr(struct kvm_lapic *apic, u32 id)
 	recalculate_apic_map(apic->vcpu->kvm);
 }
 
-static inline void kvm_apic_set_x2apic_id(struct kvm_lapic *apic, u8 id)
+static inline void kvm_apic_set_x2apic_id(struct kvm_lapic *apic, u32 id)
 {
 	u32 ldr = ((id >> 4) << 16) | (1 << (id & 0xf));
 
-	kvm_lapic_set_reg(apic, APIC_ID, id << 24);
+	kvm_lapic_set_reg(apic, APIC_ID, id);
 	kvm_lapic_set_reg(apic, APIC_LDR, ldr);
 	recalculate_apic_map(apic->vcpu->kvm);
 }
@@ -1102,12 +1102,6 @@ static u32 __apic_read(struct kvm_lapic *apic, unsigned int offset)
 		return 0;
 
 	switch (offset) {
-	case APIC_ID:
-		if (apic_x2apic_mode(apic))
-			val = kvm_apic_id(apic);
-		else
-			val = kvm_apic_id(apic) << 24;
-		break;
 	case APIC_ARBPRI:
 		apic_debug("Access APIC ARBPRI register which is for P6\n");
 		break;
@@ -1465,7 +1459,7 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
 	switch (reg) {
 	case APIC_ID:		/* Local APIC ID */
 		if (!apic_x2apic_mode(apic))
-			kvm_apic_set_id(apic, val >> 24);
+			kvm_apic_set_xapic_id(apic, val >> 24);
 		else
 			ret = 1;
 		break;
@@ -1769,7 +1763,7 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu, bool init_event)
 	hrtimer_cancel(&apic->lapic_timer.timer);
 
 	if (!init_event)
-		kvm_apic_set_id(apic, vcpu->vcpu_id);
+		kvm_apic_set_xapic_id(apic, vcpu->vcpu_id);
 	kvm_apic_set_version(apic->vcpu);
 
 	for (i = 0; i < KVM_APIC_LVT_NUM; i++)
@@ -1990,17 +1984,43 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu)
 	return vector;
 }
 
-void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
-		struct kvm_lapic_state *s)
+static int kvm_apic_state_fixup(struct kvm_vcpu *vcpu,
+		struct kvm_lapic_state *s, bool set)
+{
+	if (apic_x2apic_mode(vcpu->arch.apic)) {
+		u32 *id = (u32 *)(s->regs + APIC_ID);
+
+		if (set)
+			*id >>= 24;
+		else
+			*id <<= 24;
+	}
+
+	return 0;
+}
+
+int kvm_apic_get_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s)
+{
+	memcpy(s->regs, vcpu->arch.apic->regs, sizeof(*s));
+	return kvm_apic_state_fixup(vcpu, s, false);
+}
+
+int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s)
 {
 	struct kvm_lapic *apic = vcpu->arch.apic;
+	int r;
+
 
 	kvm_lapic_set_base(vcpu, vcpu->arch.apic_base);
 	/* set SPIV separately to get count of SW disabled APICs right */
 	apic_set_spiv(apic, *((u32 *)(s->regs + APIC_SPIV)));
+
+	r = kvm_apic_state_fixup(vcpu, s, true);
+	if (r)
+		return r;
 	memcpy(vcpu->arch.apic->regs, s->regs, sizeof *s);
-	/* call kvm_apic_set_id() to put apic into apic_map */
-	kvm_apic_set_id(apic, kvm_apic_id(apic));
+
+	recalculate_apic_map(vcpu->kvm);
 	kvm_apic_set_version(vcpu);
 
 	apic_update_ppr(apic);
@@ -2026,6 +2046,8 @@ void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
 		kvm_rtc_eoi_tracking_restore_one(vcpu);
 
 	vcpu->arch.apic_arb_prio = 0;
+
+	return 0;
 }
 
 void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)

arch/x86/kvm/lapic.h

@@ -81,8 +81,8 @@ bool kvm_irq_delivery_to_apic_fast(struct kvm *kvm, struct kvm_lapic *src,
 
 u64 kvm_get_apic_base(struct kvm_vcpu *vcpu);
 int kvm_set_apic_base(struct kvm_vcpu *vcpu, struct msr_data *msr_info);
-void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
-		struct kvm_lapic_state *s);
+int kvm_apic_get_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s);
+int kvm_apic_set_state(struct kvm_vcpu *vcpu, struct kvm_lapic_state *s);
 int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu);
 
 u64 kvm_get_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu);
@@ -202,7 +202,13 @@ static inline int kvm_lapic_latched_init(struct kvm_vcpu *vcpu)
 
 static inline u32 kvm_apic_id(struct kvm_lapic *apic)
 {
-	return (kvm_lapic_get_reg(apic, APIC_ID) >> 24) & 0xff;
+	/* To avoid a race between apic_base and following APIC_ID update when
+	 * switching to x2apic_mode, the x2apic mode returns initial x2apic id.
+	 */
+	if (apic_x2apic_mode(apic))
+		return apic->vcpu->vcpu_id;
+
+	return kvm_lapic_get_reg(apic, APIC_ID) >> 24;
 }
 
 bool kvm_apic_pending_eoi(struct kvm_vcpu *vcpu, int vector);

arch/x86/kvm/x86.c

@@ -2779,15 +2779,17 @@ static int kvm_vcpu_ioctl_get_lapic(struct kvm_vcpu *vcpu,
 	if (vcpu->arch.apicv_active)
 		kvm_x86_ops->sync_pir_to_irr(vcpu);
 
-	memcpy(s->regs, vcpu->arch.apic->regs, sizeof *s);
-
-	return 0;
+	return kvm_apic_get_state(vcpu, s);
 }
 
 static int kvm_vcpu_ioctl_set_lapic(struct kvm_vcpu *vcpu,
 				    struct kvm_lapic_state *s)
 {
-	kvm_apic_post_state_restore(vcpu, s);
+	int r;
+
+	r = kvm_apic_set_state(vcpu, s);
+	if (r)
+		return r;
 	update_cr8_intercept(vcpu);
 
 	return 0;