On Fri, Jan 13, 2023 at 12:11:32PM -0500, Matthew Rosato wrote: > @@ -462,9 +520,19 @@ static inline void vfio_device_pm_runtime_put(struct vfio_device *device) > static int vfio_device_fops_release(struct inode *inode, struct file *filep) > { > struct vfio_device *device = filep->private_data; > + struct kvm *kvm = NULL; > > vfio_device_group_close(device); > > + mutex_lock(&device->dev_set->lock); > + if (device->open_count == 0 && device->kvm) { > + kvm = device->kvm; > + device->kvm = NULL; > + } > + mutex_unlock(&device->dev_set->lock); This still doesn't seem right, another thread could have incr'd the open_count already This has to be done at the moment open_count is decremented to zero, while still under the original lock. Jason