On Thu, Apr 14, 2022 at 09:51:49AM -0400, Matthew Rosato wrote:
On 4/12/22 11:53 AM, Jason Gunthorpe wrote:
When the open_device() op is called the container_users is incremented and held incremented until close_device(). Thus, so long as drivers call functions within their open_device()/close_device() region they do not need to worry about the container_users.
These functions can all only be called between open_device()/close_device():
vfio_pin_pages() vfio_unpin_pages() vfio_dma_rw() vfio_register_notifier() vfio_unregister_notifier()
So eliminate the calls to vfio_group_add_container_user() and add a simple WARN_ON to detect mis-use by drivers.
vfio_device_fops_release decrements dev->open_count immediately before calling dev->ops->close_device, which means we could enter close_device with a dev_count of 0.
Maybe vfio_device_fops_release should handle the same way as vfio_group_get_device_fd?
if (device->open_count == 1 && device->ops->close_device) device->ops->close_device(device); device->open_count--;
Yes, thanks alot! I have nothing to test these flows on...
It matches the ordering in the only other place to call close_device.
I folded this into the patch:
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index 0f735f9f206002..29761f0cf0a227 100644 --- a/drivers/vfio/vfio.c +++ b/drivers/vfio/vfio.c @@ -1551,8 +1551,9 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)
mutex_lock(&device->dev_set->lock); vfio_assert_device_open(device); - if (!--device->open_count && device->ops->close_device) + if (device->open_count == 1 && device->ops->close_device) device->ops->close_device(device); + device->open_count--; mutex_unlock(&device->dev_set->lock);
module_put(device->dev->driver->owner);
Jason