KVM: switch irq injection/acking data structures to irq_lock

Protect irq injection/acking data structures with a separate irq_lock
mutex. This fixes the following deadlock:

CPU A                               CPU B
kvm_vm_ioctl_deassign_dev_irq()
  mutex_lock(&kvm->lock);            worker_thread()
  -> kvm_deassign_irq()                -> kvm_assigned_dev_interrupt_work_handler()
    -> deassign_host_irq()               mutex_lock(&kvm->lock);
      -> cancel_work_sync() [blocked]

[gleb: fix ia64 path]

Reported-by: Alex Williamson <alex.williamson@hp.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

3 files changed, 39 insertions, 15 deletions

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 314012323afe..4092b8dcd510 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -57,10 +57,10 @@ irqfd_inject(struct work_struct *work)
         struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
         struct kvm *kvm = irqfd->kvm;
 
-        mutex_lock(&kvm->lock);
+        mutex_lock(&kvm->irq_lock);
         kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
         kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
-        mutex_unlock(&kvm->lock);
+        mutex_unlock(&kvm->irq_lock);
 }
 
 /*
diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index ddc17f0e2f35..08a9a49481b2 100644
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -62,6 +62,8 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
         int i, r = -1;
         struct kvm_vcpu *vcpu, *lowest = NULL;
 
+        WARN_ON(!mutex_is_locked(&kvm->irq_lock));
+
         if (irq->dest_mode == 0 && irq->dest_id == 0xff &&
                         kvm_is_dm_lowest_prio(irq))
                 printk(KERN_INFO "kvm: apic: phys broadcast and lowest prio\n");
@@ -113,7 +115,7 @@ static int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
         return kvm_irq_delivery_to_apic(kvm, NULL, &irq);
 }
 
-/* This should be called with the kvm->lock mutex held
+/* This should be called with the kvm->irq_lock mutex held
  * Return value:
  *  < 0   Interrupt was ignored (masked or not delivered for other reasons)
  *  = 0   Interrupt was coalesced (previous irq is still pending)
@@ -125,6 +127,8 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level)
         unsigned long *irq_state, sig_level;
         int ret = -1;
 
+        WARN_ON(!mutex_is_locked(&kvm->irq_lock));
+
         if (irq < KVM_IOAPIC_NUM_PINS) {
                 irq_state = (unsigned long *)&kvm->arch.irq_states[irq];
 
@@ -175,19 +179,26 @@ void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
 void kvm_register_irq_ack_notifier(struct kvm *kvm,
                                    struct kvm_irq_ack_notifier *kian)
 {
+        mutex_lock(&kvm->irq_lock);
         hlist_add_head(&kian->link, &kvm->arch.irq_ack_notifier_list);
+        mutex_unlock(&kvm->irq_lock);
 }
 
-void kvm_unregister_irq_ack_notifier(struct kvm_irq_ack_notifier *kian)
+void kvm_unregister_irq_ack_notifier(struct kvm *kvm,
+                                    struct kvm_irq_ack_notifier *kian)
 {
+        mutex_lock(&kvm->irq_lock);
         hlist_del_init(&kian->link);
+        mutex_unlock(&kvm->irq_lock);
 }
 
-/* The caller must hold kvm->lock mutex */
 int kvm_request_irq_source_id(struct kvm *kvm)
 {
         unsigned long *bitmap = &kvm->arch.irq_sources_bitmap;
-        int irq_source_id = find_first_zero_bit(bitmap,
+        int irq_source_id;
+
+        mutex_lock(&kvm->irq_lock);
+        irq_source_id = find_first_zero_bit(bitmap,
                                 sizeof(kvm->arch.irq_sources_bitmap));
 
         if (irq_source_id >= sizeof(kvm->arch.irq_sources_bitmap)) {
@@ -197,6 +208,7 @@ int kvm_request_irq_source_id(struct kvm *kvm)
 
         ASSERT(irq_source_id != KVM_USERSPACE_IRQ_SOURCE_ID);
         set_bit(irq_source_id, bitmap);
+        mutex_unlock(&kvm->irq_lock);
 
         return irq_source_id;
 }
@@ -207,6 +219,7 @@ void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id)
 
         ASSERT(irq_source_id != KVM_USERSPACE_IRQ_SOURCE_ID);
 
+        mutex_lock(&kvm->irq_lock);
         if (irq_source_id < 0 ||
             irq_source_id >= sizeof(kvm->arch.irq_sources_bitmap)) {
                 printk(KERN_ERR "kvm: IRQ source ID out of range!\n");
@@ -215,19 +228,24 @@ void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id)
         for (i = 0; i < KVM_IOAPIC_NUM_PINS; i++)
                 clear_bit(irq_source_id, &kvm->arch.irq_states[i]);
         clear_bit(irq_source_id, &kvm->arch.irq_sources_bitmap);
+        mutex_unlock(&kvm->irq_lock);
 }
 
 void kvm_register_irq_mask_notifier(struct kvm *kvm, int irq,
                                     struct kvm_irq_mask_notifier *kimn)
 {
+        mutex_lock(&kvm->irq_lock);
         kimn->irq = irq;
         hlist_add_head(&kimn->link, &kvm->mask_notifier_list);
+        mutex_unlock(&kvm->irq_lock);
 }
 
 void kvm_unregister_irq_mask_notifier(struct kvm *kvm, int irq,
                                       struct kvm_irq_mask_notifier *kimn)
 {
+        mutex_lock(&kvm->irq_lock);
         hlist_del(&kimn->link);
+        mutex_unlock(&kvm->irq_lock);
 }
 
 void kvm_fire_mask_notifiers(struct kvm *kvm, int irq, bool mask)
@@ -235,6 +253,8 @@ void kvm_fire_mask_notifiers(struct kvm *kvm, int irq, bool mask)
         struct kvm_irq_mask_notifier *kimn;
         struct hlist_node *n;
 
+        WARN_ON(!mutex_is_locked(&kvm->irq_lock));
+
         hlist_for_each_entry(kimn, n, &kvm->mask_notifier_list, link)
                 if (kimn->irq == irq)
                         kimn->func(kimn, mask);
@@ -250,7 +270,9 @@ static void __kvm_free_irq_routing(struct list_head *irq_routing)
 
 void kvm_free_irq_routing(struct kvm *kvm)
 {
+        mutex_lock(&kvm->irq_lock);
         __kvm_free_irq_routing(&kvm->irq_routing);
+        mutex_unlock(&kvm->irq_lock);
 }
 
 static int setup_routing_entry(struct kvm_kernel_irq_routing_entry *e,
@@ -325,13 +347,13 @@ int kvm_set_irq_routing(struct kvm *kvm,
                 e = NULL;
         }
 
-        mutex_lock(&kvm->lock);
+        mutex_lock(&kvm->irq_lock);
         list_splice(&kvm->irq_routing, &tmp);
         INIT_LIST_HEAD(&kvm->irq_routing);
         list_splice(&irq_list, &kvm->irq_routing);
         INIT_LIST_HEAD(&irq_list);
         list_splice(&tmp, &irq_list);
-        mutex_unlock(&kvm->lock);
+        mutex_unlock(&kvm->irq_lock);
 
         r = 0;
 
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index d47e660fb709..0d481b282448 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -62,6 +62,12 @@
 MODULE_AUTHOR("Qumranet");
 MODULE_LICENSE("GPL");
 
+/*
+ * Ordering of locks:
+ *
+ *              kvm->lock --> kvm->irq_lock
+ */
+
 DEFINE_SPINLOCK(kvm_lock);
 LIST_HEAD(vm_list);
 
@@ -126,11 +132,7 @@ static void kvm_assigned_dev_interrupt_work_handler(struct work_struct *work)
                                     interrupt_work);
         kvm = assigned_dev->kvm;
 
-        /* This is taken to safely inject irq inside the guest. When
-         * the interrupt injection (or the ioapic code) uses a
-         * finer-grained lock, update this
-         */
-        mutex_lock(&kvm->lock);
+        mutex_lock(&kvm->irq_lock);
         spin_lock_irq(&assigned_dev->assigned_dev_lock);
         if (assigned_dev->irq_requested_type & KVM_DEV_IRQ_HOST_MSIX) {
                 struct kvm_guest_msix_entry *guest_entries =
@@ -149,7 +151,7 @@ static void kvm_assigned_dev_interrupt_work_handler(struct work_struct *work)
                             assigned_dev->guest_irq, 1);
 
         spin_unlock_irq(&assigned_dev->assigned_dev_lock);
-        mutex_unlock(&assigned_dev->kvm->lock);
+        mutex_unlock(&assigned_dev->kvm->irq_lock);
 }
 
 static irqreturn_t kvm_assigned_dev_intr(int irq, void *dev_id)
@@ -207,7 +209,7 @@ static void kvm_assigned_dev_ack_irq(struct kvm_irq_ack_notifier *kian)
 static void deassign_guest_irq(struct kvm *kvm,
                                struct kvm_assigned_dev_kernel *assigned_dev)
 {
-        kvm_unregister_irq_ack_notifier(&assigned_dev->ack_notifier);
+        kvm_unregister_irq_ack_notifier(kvm, &assigned_dev->ack_notifier);
         assigned_dev->ack_notifier.gsi = -1;
 
         if (assigned_dev->irq_source_id != -1)