[PATCH 05/12] Make the IOAPIC lock a spinlock.

[Chris Lalancette <clalance@xxxxxxxxxx>]

In order to be able to call kvm_set_irq from an interrupt
context, the IOAPIC lock can't be a (possibly sleeping) mutex.
Convert it to a spinlock.

Signed-off-by: Chris Lalancette <clalance@xxxxxxxxxx>
---
 virt/kvm/ioapic.c |   40 +++++++++++++++++++++++++---------------
 virt/kvm/ioapic.h |    2 +-
 2 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index fd52949..3d68826 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -192,8 +192,9 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
 	u32 mask = 1 << irq;
 	union kvm_ioapic_redirect_entry entry;
 	int ret = 1;
+	unsigned long flags;
 
-	mutex_lock(&ioapic->lock);
+	spin_lock_irqsave(&ioapic->lock, flags);
 	if (irq >= 0 && irq < IOAPIC_NUM_PINS) {
 		entry = ioapic->redirtbl[irq];
 		level ^= entry.fields.polarity;
@@ -210,7 +211,7 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
 		}
 		trace_kvm_ioapic_set_irq(entry.bits, irq, ret == 0);
 	}
-	mutex_unlock(&ioapic->lock);
+	spin_unlock_irqrestore(&ioapic->lock, flags);
 
 	return ret;
 }
@@ -234,9 +235,9 @@ static void __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int vector,
 		 * is dropped it will be put into irr and will be delivered
 		 * after ack notifier returns.
 		 */
-		mutex_unlock(&ioapic->lock);
+		spin_unlock(&ioapic->lock);
 		kvm_notify_acked_irq(ioapic->kvm, KVM_IRQCHIP_IOAPIC, i);
-		mutex_lock(&ioapic->lock);
+		spin_lock(&ioapic->lock);
 
 		if (trigger_mode != IOAPIC_LEVEL_TRIG)
 			continue;
@@ -251,10 +252,11 @@ static void __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int vector,
 void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode)
 {
 	struct kvm_ioapic *ioapic = kvm->arch.vioapic;
+	unsigned long flags;
 
-	mutex_lock(&ioapic->lock);
+	spin_lock_irqsave(&ioapic->lock, flags);
 	__kvm_ioapic_update_eoi(ioapic, vector, trigger_mode);
-	mutex_unlock(&ioapic->lock);
+	spin_unlock_irqrestore(&ioapic->lock, flags);
 }
 
 static inline struct kvm_ioapic *to_ioapic(struct kvm_io_device *dev)
@@ -273,6 +275,8 @@ static int ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
 {
 	struct kvm_ioapic *ioapic = to_ioapic(this);
 	u32 result;
+	unsigned long flags;
+
 	if (!ioapic_in_range(ioapic, addr))
 		return -EOPNOTSUPP;
 
@@ -280,7 +284,7 @@ static int ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
 	ASSERT(!(addr & 0xf));	/* check alignment */
 
 	addr &= 0xff;
-	mutex_lock(&ioapic->lock);
+	spin_lock_irqsave(&ioapic->lock, flags);
 	switch (addr) {
 	case IOAPIC_REG_SELECT:
 		result = ioapic->ioregsel;
@@ -294,7 +298,7 @@ static int ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
 		result = 0;
 		break;
 	}
-	mutex_unlock(&ioapic->lock);
+	spin_unlock_irqrestore(&ioapic->lock, flags);
 
 	switch (len) {
 	case 8:
@@ -316,6 +320,8 @@ static int ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
 {
 	struct kvm_ioapic *ioapic = to_ioapic(this);
 	u32 data;
+	unsigned long flags;
+
 	if (!ioapic_in_range(ioapic, addr))
 		return -EOPNOTSUPP;
 
@@ -331,7 +337,7 @@ static int ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
 	}
 
 	addr &= 0xff;
-	mutex_lock(&ioapic->lock);
+	spin_lock_irqsave(&ioapic->lock, flags);
 	switch (addr) {
 	case IOAPIC_REG_SELECT:
 		ioapic->ioregsel = data;
@@ -349,7 +355,7 @@ static int ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
 	default:
 		break;
 	}
-	mutex_unlock(&ioapic->lock);
+	spin_unlock_irqrestore(&ioapic->lock, flags);
 	return 0;
 }
 
@@ -378,7 +384,7 @@ int kvm_ioapic_init(struct kvm *kvm)
 	ioapic = kzalloc(sizeof(struct kvm_ioapic), GFP_KERNEL);
 	if (!ioapic)
 		return -ENOMEM;
-	mutex_init(&ioapic->lock);
+	spin_lock_init(&ioapic->lock);
 	kvm->arch.vioapic = ioapic;
 	kvm_ioapic_reset(ioapic);
 	kvm_iodevice_init(&ioapic->dev, &ioapic_mmio_ops);
@@ -393,23 +399,27 @@ int kvm_ioapic_init(struct kvm *kvm)
 int kvm_get_ioapic(struct kvm *kvm, struct kvm_ioapic_state *state)
 {
 	struct kvm_ioapic *ioapic = ioapic_irqchip(kvm);
+	unsigned long flags;
+
 	if (!ioapic)
 		return -EINVAL;
 
-	mutex_lock(&ioapic->lock);
+	spin_lock_irqsave(&ioapic->lock, flags);
 	memcpy(state, ioapic, sizeof(struct kvm_ioapic_state));
-	mutex_unlock(&ioapic->lock);
+	spin_unlock_irqrestore(&ioapic->lock, flags);
 	return 0;
 }
 
 int kvm_set_ioapic(struct kvm *kvm, struct kvm_ioapic_state *state)
 {
 	struct kvm_ioapic *ioapic = ioapic_irqchip(kvm);
+	unsigned long flags;
+
 	if (!ioapic)
 		return -EINVAL;
 
-	mutex_lock(&ioapic->lock);
+	spin_lock_irqsave(&ioapic->lock, flags);
 	memcpy(ioapic, state, sizeof(struct kvm_ioapic_state));
-	mutex_unlock(&ioapic->lock);
+	spin_unlock_irqrestore(&ioapic->lock, flags);
 	return 0;
 }
diff --git a/virt/kvm/ioapic.h b/virt/kvm/ioapic.h
index 419c43b..5b4f756 100644
--- a/virt/kvm/ioapic.h
+++ b/virt/kvm/ioapic.h
@@ -45,7 +45,7 @@ struct kvm_ioapic {
 	struct kvm_io_device dev;
 	struct kvm *kvm;
 	void (*ack_notifier)(void *opaque, int irq);
-	struct mutex lock;
+	spinlock_t lock;
 };
 
 #ifdef DEBUG
-- 
1.6.5.2

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