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>

1 files changed, 9 insertions, 7 deletions

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)