linux-kernel - [PATCH v2 2/6] KVM: x86: decouple irqchip_in_kernel() and pic

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Date:   Fri, 16 Dec 2016 16:10:02 +0100
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH v2 2/6] 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.

Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 v2: change two bools into one enum and rename everything [Paolo]
---
 arch/x86/include/asm/kvm_host.h |  8 +++++++-
 arch/x86/kvm/irq.h              | 15 ++++++++-------
 arch/x86/kvm/x86.c              |  5 +++--
 3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7892530cbacf..d3acd295446d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -715,6 +715,12 @@ 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;
@@ -787,7 +793,7 @@ struct kvm_arch {
 
 	u64 disabled_quirks;
 
-	bool irqchip_split;
+	enum kvm_irqchip_mode irqchip_mode;
 	u8 nr_reserved_ioapic_pins;
 
 	bool disabled_lapic_found;
diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
index 035731eb3897..79cfc945125c 100644
--- a/arch/x86/kvm/irq.h
+++ b/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_kernel(struct kvm *kvm)
+{
+	return kvm->arch.irqchip_mode == KVM_IRQCHIP_KERNEL;
 }
 
 static inline int irqchip_in_kernel(struct kvm *kvm)
 {
-	struct kvm_pic *vpic = pic_irqchip(kvm);
-	bool ret;
+	bool ret = irqchip_kernel(kvm) || irqchip_split(kvm);
 
-	ret = (vpic != NULL);
-	ret |= irqchip_split(kvm);
-
-	/* Read vpic before kvm->irq_routing.  */
+	/* Matches with wmb after initializing kvm->irq_routing. */
 	smp_rmb();
 	return ret;
 }
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e670591337af..a8dbfb4129c5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3872,7 +3872,7 @@ 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:
@@ -3966,8 +3966,9 @@ 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);
-- 
2.11.0