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>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b5af881..7db071b 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -64,7 +64,7 @@
/*
* Ordering of locks:
*
- * kvm->slots_lock --> kvm->lock --> kvm->irq_lock
+ * kvm->lock --> kvm->slots_lock --> kvm->irq_lock
*/
DEFINE_SPINLOCK(kvm_lock);