[patch 3/4] KVM: introduce irq_lock, use it to protect ioapic

[Marcelo Tosatti <mtosatti@redhat.com>]

[-- Attachment #1: ioapic-lock --]
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Subject says it all.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: kvm-irqlock/include/linux/kvm_host.h
===================================================================
--- kvm-irqlock.orig/include/linux/kvm_host.h
+++ kvm-irqlock/include/linux/kvm_host.h
@@ -123,7 +123,6 @@ struct kvm_kernel_irq_routing_entry {
 };
 
 struct kvm {
-	struct mutex lock; /* protects the vcpus array and APIC accesses */
 	spinlock_t mmu_lock;
 	struct rw_semaphore slots_lock;
 	struct mm_struct *mm; /* userspace tied to this vm */
@@ -132,6 +131,12 @@ struct kvm {
 					KVM_PRIVATE_MEM_SLOTS];
 	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
 	struct list_head vm_list;
+	struct mutex lock; /*
+			    * - protects mmio_bus, pio_bus.
+			    * - protects a few concurrent ioctl's (FIXME).
+			    * - protects concurrent create_vcpu, but
+			    *   kvm->vcpus walkers do it locklessly (FIXME).
+			    */
 	struct kvm_io_bus mmio_bus;
 	struct kvm_io_bus pio_bus;
 	struct list_head irqfds;
@@ -143,6 +148,7 @@ struct kvm {
 	struct kvm_coalesced_mmio_ring *coalesced_mmio_ring;
 #endif
 
+	struct mutex irq_lock; /* protects high level irq logic, ioapic */
 #ifdef CONFIG_HAVE_KVM_IRQCHIP
 	struct list_head irq_routing; /* of kvm_kernel_irq_routing_entry */
 	struct hlist_head mask_notifier_list;
Index: kvm-irqlock/virt/kvm/ioapic.c
===================================================================
--- kvm-irqlock.orig/virt/kvm/ioapic.c
+++ kvm-irqlock/virt/kvm/ioapic.c
@@ -225,6 +225,10 @@ static int ioapic_in_range(struct kvm_io
 {
 	struct kvm_ioapic *ioapic = (struct kvm_ioapic *)this->private;
 
+	/*
+	 * Lockless check for ioapic->base_address on the hazy assumption
+	 * it does not change during the lifetime of a VM.
+	 */
 	return ((addr >= ioapic->base_address &&
 		 (addr < ioapic->base_address + IOAPIC_MEM_LENGTH)));
 }
@@ -238,6 +242,7 @@ static void ioapic_mmio_read(struct kvm_
 	ioapic_debug("addr %lx\n", (unsigned long)addr);
 	ASSERT(!(addr & 0xf));	/* check alignment */
 
+	mutex_lock(&ioapic->kvm->irq_lock);
 	addr &= 0xff;
 	switch (addr) {
 	case IOAPIC_REG_SELECT:
@@ -264,6 +269,7 @@ static void ioapic_mmio_read(struct kvm_
 	default:
 		printk(KERN_WARNING "ioapic: wrong length %d\n", len);
 	}
+	mutex_unlock(&ioapic->kvm->irq_lock);
 }
 
 static void ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
@@ -275,6 +281,8 @@ static void ioapic_mmio_write(struct kvm
 	ioapic_debug("ioapic_mmio_write addr=%p len=%d val=%p\n",
 		     (void*)addr, len, val);
 	ASSERT(!(addr & 0xf));	/* check alignment */
+
+	mutex_lock(&ioapic->kvm->irq_lock);
 	if (len == 4 || len == 8)
 		data = *(u32 *) val;
 	else {
@@ -300,6 +308,7 @@ static void ioapic_mmio_write(struct kvm
 	default:
 		break;
 	}
+	mutex_unlock(&ioapic->kvm->irq_lock);
 }
 
 void kvm_ioapic_reset(struct kvm_ioapic *ioapic)
Index: kvm-irqlock/virt/kvm/kvm_main.c
===================================================================
--- kvm-irqlock.orig/virt/kvm/kvm_main.c
+++ kvm-irqlock/virt/kvm/kvm_main.c
@@ -985,6 +985,7 @@ static struct kvm *kvm_create_vm(void)
 	kvm_io_bus_init(&kvm->pio_bus);
 	INIT_LIST_HEAD(&kvm->irqfds);
 	mutex_init(&kvm->lock);
+	mutex_init(&kvm->irq_lock);
 	kvm_io_bus_init(&kvm->mmio_bus);
 	init_rwsem(&kvm->slots_lock);
 	atomic_set(&kvm->users_count, 1);

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