linux-kernel - Re: [PATCH 2/6] KVM: x86: decouple irqchip_in_kernel() and pic

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Date:   Thu, 24 Nov 2016 18:21:04 +0100
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 2/6] KVM: x86: decouple irqchip_in_kernel() and
 pic_irqchip()

2016-11-24 11:55-0500, Paolo Bonzini:
>> irqchip_in_kernel() tried to save a bit by reusing pic_irqchip(), but it
>> just complicated the code.
>> Add kvm->arch.irqchip_kvm that matches kvm->arch.irqchip_split.
>> (Turning them into an exclusive type would be nicer.)
> 
> Then do it. ;)

It is hard to name! :)

I would squash something like this if the names were ok:

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 929228ec2839..726235f0e3f3 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -706,6 +706,12 @@ struct kvm_hv {
 	HV_REFERENCE_TSC_PAGE tsc_ref;
 };
 
+enum kvm_kernel_irqchip {
+	KVM_IRQCHIP_NONE,
+	KVM_IRQCHIP_KVM,          /* created in KVM_CREATE_IRQCHIP */
+	KVM_IRQCHIP_SPLIT,        /* created in KVM_CAP_SPLIT_IRQCHIP */
+};
+
 struct kvm_arch {
 	unsigned int n_used_mmu_pages;
 	unsigned int n_requested_mmu_pages;
@@ -778,8 +784,7 @@ struct kvm_arch {
 
 	u64 disabled_quirks;
 
-	bool irqchip_kvm;
-	bool irqchip_split;
+	enum kvm_kernel_irqchip irqchip;
 	u8 nr_reserved_ioapic_pins;
 
 	bool disabled_lapic_found;
diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
index a80515e38645..f90ca9e0affc 100644
--- a/arch/x86/kvm/irq.h
+++ b/arch/x86/kvm/irq.h
@@ -93,12 +93,12 @@ 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 == KVM_IRQCHIP_SPLIT;
 }
 
 static inline int irqchip_kvm(struct kvm *kvm)
 {
-	return kvm->arch.irqchip_kvm;
+	return kvm->arch.irqchip == KVM_IRQCHIP_KVM;
 }
 
 static inline int irqchip_in_kernel(struct kvm *kvm)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4c364a13b17c..99c63b73dd35 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3834,7 +3834,7 @@ 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 = KVM_IRQCHIP_SPLIT;
 		kvm->arch.nr_reserved_ioapic_pins = cap->args[0];
 		r = 0;
 split_irqchip_unlock:
@@ -3931,7 +3931,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		}
 		/* Write kvm->irq_routing before enabling irqchip_in_kernel. */
 		smp_wmb();
-		kvm->arch.irqchip_kvm = true;
+		kvm->arch.irqchip = KVM_IRQCHIP_KVM;
 	create_irqchip_unlock:
 		mutex_unlock(&kvm->lock);
 		break;