KVM: x86: decouple irqchip_in_kernel() and pic_irqchip()

irqchip_in_kernel() tried to save a bit by reusing pic_irqchip(), but it
just complicated the code.
Add a separate state for the irqchip mode.
Reviewed-by: David Hildenbrand <david@redhat.com>
[Used Paolo's version of condition in irqchip_in_kernel().]
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -716,6 +716,12 @@ struct kvm_hv {
 	HV_REFERENCE_TSC_PAGE tsc_ref;
 };
 
+enum kvm_irqchip_mode {
+	KVM_IRQCHIP_NONE,
+	KVM_IRQCHIP_KERNEL,       /* created with KVM_CREATE_IRQCHIP */
+	KVM_IRQCHIP_SPLIT,        /* created with KVM_CAP_SPLIT_IRQCHIP */
+};
+
 struct kvm_arch {
 	unsigned int n_used_mmu_pages;
 	unsigned int n_requested_mmu_pages;
@@ -788,7 +794,7 @@ struct kvm_arch {
 
 	u64 disabled_quirks;
 
-	bool irqchip_split;
+	enum kvm_irqchip_mode irqchip_mode;
 	u8 nr_reserved_ioapic_pins;
 
 	bool disabled_lapic_found;

arch/x86/kvm/irq.h

@@ -93,18 +93,19 @@ static inline int pic_in_kernel(struct kvm *kvm)
 
 static inline int irqchip_split(struct kvm *kvm)
 {
-	return kvm->arch.irqchip_split;
+	return kvm->arch.irqchip_mode == KVM_IRQCHIP_SPLIT;
 }
 
-static inline int irqchip_in_kernel(struct kvm *kvm)
+static inline int irqchip_kernel(struct kvm *kvm)
 {
-	struct kvm_pic *vpic = pic_irqchip(kvm);
-	bool ret;
+	return kvm->arch.irqchip_mode == KVM_IRQCHIP_KERNEL;
+}
 
-	ret = (vpic != NULL);
-	ret |= irqchip_split(kvm);
+static inline int irqchip_in_kernel(struct kvm *kvm)
+{
+	bool ret = kvm->arch.irqchip_mode != KVM_IRQCHIP_NONE;
 
-	/* Read vpic before kvm->irq_routing.  */
+	/* Matches with wmb after initializing kvm->irq_routing. */
 	smp_rmb();
 	return ret;
 }

arch/x86/kvm/x86.c

@@ -3894,7 +3894,7 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 			goto split_irqchip_unlock;
 		/* Pairs with irqchip_in_kernel. */
 		smp_wmb();
-		kvm->arch.irqchip_split = true;
+		kvm->arch.irqchip_mode = KVM_IRQCHIP_SPLIT;
 		kvm->arch.nr_reserved_ioapic_pins = cap->args[0];
 		r = 0;
 split_irqchip_unlock:
@@ -3988,8 +3988,9 @@ long kvm_arch_vm_ioctl(struct file *filp,
 			mutex_unlock(&kvm->slots_lock);
 			goto create_irqchip_unlock;
 		}
-		/* Write kvm->irq_routing before kvm->arch.vpic.  */
+		/* Write kvm->irq_routing before enabling irqchip_in_kernel. */
 		smp_wmb();
+		kvm->arch.irqchip_mode = KVM_IRQCHIP_KERNEL;
 		kvm->arch.vpic = vpic;
 	create_irqchip_unlock:
 		mutex_unlock(&kvm->lock);