KVM: x86: Change __kvm_apic_update_irr() to also return if max IRR updated

This commit doesn't change semantics.
It is done as a preparation for future commits.

Signed-off-by: Liran Alon <liran.alon@oracle.com>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@oracle.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Signed-off-by: Liam Merwick <liam.merwick@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/lapic.c

@@ -364,32 +364,41 @@ static u8 count_vectors(void *bitmap)
 	return count;
 }
 
-int __kvm_apic_update_irr(u32 *pir, void *regs)
+bool __kvm_apic_update_irr(u32 *pir, void *regs, int *max_irr)
 {
 	u32 i, vec;
-	u32 pir_val, irr_val;
-	int max_irr = -1;
+	u32 pir_val, irr_val, prev_irr_val;
+	int max_updated_irr;
+
+	max_updated_irr = -1;
+	*max_irr = -1;
 
 	for (i = vec = 0; i <= 7; i++, vec += 32) {
 		pir_val = READ_ONCE(pir[i]);
 		irr_val = *((u32 *)(regs + APIC_IRR + i * 0x10));
 		if (pir_val) {
+			prev_irr_val = irr_val;
 			irr_val |= xchg(&pir[i], 0);
 			*((u32 *)(regs + APIC_IRR + i * 0x10)) = irr_val;
+			if (prev_irr_val != irr_val) {
+				max_updated_irr =
+					__fls(irr_val ^ prev_irr_val) + vec;
+			}
 		}
 		if (irr_val)
-			max_irr = __fls(irr_val) + vec;
+			*max_irr = __fls(irr_val) + vec;
 	}
 
-	return max_irr;
+	return ((max_updated_irr != -1) &&
+		(max_updated_irr == *max_irr));
 }
 EXPORT_SYMBOL_GPL(__kvm_apic_update_irr);
 
-int kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir)
+bool kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir, int *max_irr)
 {
 	struct kvm_lapic *apic = vcpu->arch.apic;
 
-	return __kvm_apic_update_irr(pir, apic->regs);
+	return __kvm_apic_update_irr(pir, apic->regs, max_irr);
 }
 EXPORT_SYMBOL_GPL(kvm_apic_update_irr);
 

arch/x86/kvm/lapic.h

@@ -75,8 +75,8 @@ int kvm_lapic_reg_read(struct kvm_lapic *apic, u32 offset, int len,
 bool kvm_apic_match_dest(struct kvm_vcpu *vcpu, struct kvm_lapic *source,
 			   int short_hand, unsigned int dest, int dest_mode);
 
-int __kvm_apic_update_irr(u32 *pir, void *regs);
-int kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir);
+bool __kvm_apic_update_irr(u32 *pir, void *regs, int *max_irr);
+bool kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 *pir, int *max_irr);
 void kvm_apic_update_ppr(struct kvm_vcpu *vcpu);
 int kvm_apic_set_irq(struct kvm_vcpu *vcpu, struct kvm_lapic_irq *irq,
 		     struct dest_map *dest_map);

arch/x86/kvm/vmx.c

@@ -5085,7 +5085,8 @@ static void vmx_complete_nested_posted_interrupt(struct kvm_vcpu *vcpu)
 	max_irr = find_last_bit((unsigned long *)vmx->nested.pi_desc->pir, 256);
 	if (max_irr != 256) {
 		vapic_page = kmap(vmx->nested.virtual_apic_page);
-		__kvm_apic_update_irr(vmx->nested.pi_desc->pir, vapic_page);
+		__kvm_apic_update_irr(vmx->nested.pi_desc->pir,
+			vapic_page, &max_irr);
 		kunmap(vmx->nested.virtual_apic_page);
 
 		status = vmcs_read16(GUEST_INTR_STATUS);
@@ -8986,7 +8987,7 @@ static int vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
 		 * But on x86 this is just a compiler barrier anyway.
 		 */
 		smp_mb__after_atomic();
-		max_irr = kvm_apic_update_irr(vcpu, vmx->pi_desc.pir);
+		kvm_apic_update_irr(vcpu, vmx->pi_desc.pir, &max_irr);
 	} else {
 		max_irr = kvm_lapic_find_highest_irr(vcpu);
 	}