[PATCH v1 06/11] KVM: x86: use hardware-compatible format for APIC ID register

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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@xxxxxxxxxx>
---
 v1:
 * drop big endian format in lapic get/set ioctl [Paolo]
 * exclude APICv optimization of APIC ID register
 * rename __kvm_apic_state_fixup() parameter from 'restore' to 'set'

 arch/x86/kvm/lapic.c | 44 ++++++++++++++++++++++++++++++++------------
 arch/x86/kvm/lapic.h |  7 ++++++-
 arch/x86/kvm/x86.c   |  2 ++
 3 files changed, 40 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 4296bb7353ff..d914b5351fdc 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -224,7 +224,7 @@ 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);
@@ -236,11 +236,11 @@ 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);
 }
@@ -1096,12 +1096,6 @@ 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;
@@ -1459,7 +1453,7 @@ 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;
@@ -1731,8 +1725,10 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value)
 		if (value & X2APIC_ENABLE) {
 			kvm_apic_set_x2apic_id(apic, vcpu->vcpu_id);
 			kvm_x86_ops->set_virtual_x2apic_mode(vcpu, true);
-		} else
+		} else {
+			kvm_apic_set_xapic_id(apic, vcpu->vcpu_id);
 			kvm_x86_ops->set_virtual_x2apic_mode(vcpu, false);
+		}
 	}
 
 	apic->base_address = apic->vcpu->arch.apic_base &
@@ -1763,7 +1759,7 @@ 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++)
@@ -1984,6 +1980,30 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu)
 	return vector;
 }
 
+static void __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;
+	}
+}
+
+void kvm_apic_state_get_fixup(struct kvm_vcpu *vcpu,
+		struct kvm_lapic_state *s)
+{
+	__kvm_apic_state_fixup(vcpu, s, false);
+}
+
+void kvm_apic_state_set_fixup(struct kvm_vcpu *vcpu,
+		struct kvm_lapic_state *s)
+{
+	__kvm_apic_state_fixup(vcpu, s, true);
+}
+
 void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
 		struct kvm_lapic_state *s)
 {
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 8d811139d2b3..8d33cc56ee62 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -81,6 +81,10 @@ 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_state_get_fixup(struct kvm_vcpu *vcpu,
+		struct kvm_lapic_state *s);
+void kvm_apic_state_set_fixup(struct kvm_vcpu *vcpu,
+		struct kvm_lapic_state *s);
 void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
 		struct kvm_lapic_state *s);
 int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu);
@@ -202,7 +206,8 @@ 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;
+	u32 id = kvm_lapic_get_reg(apic, APIC_ID);
+	return apic_x2apic_mode(apic) ? id : id >> 24;
 }
 
 bool kvm_apic_pending_eoi(struct kvm_vcpu *vcpu, int vector);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0cc6cf834cdd..043f110f2210 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2780,6 +2780,7 @@ static int kvm_vcpu_ioctl_get_lapic(struct kvm_vcpu *vcpu,
 		kvm_x86_ops->sync_pir_to_irr(vcpu);
 
 	memcpy(s->regs, vcpu->arch.apic->regs, sizeof *s);
+	kvm_apic_state_get_fixup(vcpu, s);
 
 	return 0;
 }
@@ -2787,6 +2788,7 @@ static int kvm_vcpu_ioctl_get_lapic(struct kvm_vcpu *vcpu,
 static int kvm_vcpu_ioctl_set_lapic(struct kvm_vcpu *vcpu,
 				    struct kvm_lapic_state *s)
 {
+	kvm_apic_state_set_fixup(vcpu, s);
 	kvm_apic_post_state_restore(vcpu, s);
 	update_cr8_intercept(vcpu);
 
-- 
2.9.0

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