KVM: Convert intx_mask_lock to spin lock

As kvm_notify_acked_irq calls kvm_assigned_dev_ack_irq under
rcu_read_lock, we cannot use a mutex in the latter function. Switch to a
spin lock to address this.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

2 files changed, 8 insertions, 8 deletions

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index ec171c1d0878..40bb1c661a6e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -556,7 +556,7 @@ struct kvm_assigned_dev_kernel {
         struct pci_dev *dev;
         struct kvm *kvm;
         spinlock_t intx_lock;
-        struct mutex intx_mask_lock;
+        spinlock_t intx_mask_lock;
         char irq_name[32];
         struct pci_saved_state *pci_saved_state;
 };
diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
index 08e05715df72..01f572c10c71 100644
--- a/virt/kvm/assigned-dev.c
+++ b/virt/kvm/assigned-dev.c
@@ -77,11 +77,11 @@ kvm_assigned_dev_raise_guest_irq(struct kvm_assigned_dev_kernel *assigned_dev,
 {
         if (unlikely(assigned_dev->irq_requested_type &
                      KVM_DEV_IRQ_GUEST_INTX)) {
-                mutex_lock(&assigned_dev->intx_mask_lock);
+                spin_lock(&assigned_dev->intx_mask_lock);
                 if (!(assigned_dev->flags & KVM_DEV_ASSIGN_MASK_INTX))
                         kvm_set_irq(assigned_dev->kvm,
                                     assigned_dev->irq_source_id, vector, 1);
-                mutex_unlock(&assigned_dev->intx_mask_lock);
+                spin_unlock(&assigned_dev->intx_mask_lock);
         } else
                 kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id,
                             vector, 1);
@@ -141,7 +141,7 @@ static void kvm_assigned_dev_ack_irq(struct kvm_irq_ack_notifier *kian)
 
         kvm_set_irq(dev->kvm, dev->irq_source_id, dev->guest_irq, 0);
 
-        mutex_lock(&dev->intx_mask_lock);
+        spin_lock(&dev->intx_mask_lock);
 
         if (!(dev->flags & KVM_DEV_ASSIGN_MASK_INTX)) {
                 bool reassert = false;
@@ -165,7 +165,7 @@ static void kvm_assigned_dev_ack_irq(struct kvm_irq_ack_notifier *kian)
                                     dev->guest_irq, 1);
         }
 
-        mutex_unlock(&dev->intx_mask_lock);
+        spin_unlock(&dev->intx_mask_lock);
 }
 
 static void deassign_guest_irq(struct kvm *kvm,
@@ -707,7 +707,7 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
         match->flags = assigned_dev->flags;
         match->dev = dev;
         spin_lock_init(&match->intx_lock);
-        mutex_init(&match->intx_mask_lock);
+        spin_lock_init(&match->intx_mask_lock);
         match->irq_source_id = -1;
         match->kvm = kvm;
         match->ack_notifier.irq_acked = kvm_assigned_dev_ack_irq;
@@ -868,7 +868,7 @@ static int kvm_vm_ioctl_set_pci_irq_mask(struct kvm *kvm,
                 goto out;
         }
 
-        mutex_lock(&match->intx_mask_lock);
+        spin_lock(&match->intx_mask_lock);
 
         match->flags &= ~KVM_DEV_ASSIGN_MASK_INTX;
         match->flags |= assigned_dev->flags & KVM_DEV_ASSIGN_MASK_INTX;
@@ -895,7 +895,7 @@ static int kvm_vm_ioctl_set_pci_irq_mask(struct kvm *kvm,
                 }
         }
 
-        mutex_unlock(&match->intx_mask_lock);
+        spin_unlock(&match->intx_mask_lock);
 
 out:
         mutex_unlock(&kvm->lock);