KVM: Fix possible circular locking in kvm_vm_ioctl_assign_device()

One possible order is:

KVM_CREATE_IRQCHIP ioctl(took kvm->lock) -> kvm_iobus_register_dev() ->
down_write(kvm->slots_lock).

The other one is in kvm_vm_ioctl_assign_device(), which take kvm->slots_lock
first, then kvm->lock.

Update the comment of lock order as well.

Observe it due to kernel locking debug warnings.

Cc: stable@kernel.org
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b5af88167613..7db071ba466c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -64,7 +64,7 @@ MODULE_LICENSE("GPL");
 /*
  * Ordering of locks:
  *
- *              kvm->slots_lock --> kvm->lock --> kvm->irq_lock
+ *              kvm->lock --> kvm->slots_lock --> kvm->irq_lock
  */
 
 DEFINE_SPINLOCK(kvm_lock);