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Commit d24cdbfd authored by Alex Williamson's avatar Alex Williamson
Browse files

vfio-pci: Avoid deadlock on remove 



If an attempt is made to unbind a device from vfio-pci while that
device is in use, the request is blocked until the device becomes
unused.  Unfortunately, that unbind path still grabs the device_lock,
which certain things like __pci_reset_function() also want to take.
This means we need to try to acquire the locks ourselves and use the
pre-locked version, __pci_reset_function_locked().

Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent c6401930

drivers/vfio/pci/vfio_pci.c

+21 −2
Original line number Diff line number Diff line
@@ -137,8 +137,27 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev) 
	 */

	pci_write_config_word(pdev, PCI_COMMAND, PCI_COMMAND_INTX_DISABLE);



	if (vdev->reset_works)

		__pci_reset_function(pdev);

	/*

	 * Careful, device_lock may already be held.  This is the case if

	 * a driver unbind is blocked.  Try to get the locks ourselves to

	 * prevent a deadlock.

	 */

	if (vdev->reset_works) {

		bool reset_done = false;



		if (pci_cfg_access_trylock(pdev)) {

			if (device_trylock(&pdev->dev)) {

				__pci_reset_function_locked(pdev);

				reset_done = true;

				device_unlock(&pdev->dev);

			}

			pci_cfg_access_unlock(pdev);

		}



		if (!reset_done)

			pr_warn("%s: Unable to acquire locks for reset of %s\n",

				__func__, dev_name(&pdev->dev));

	}



	pci_restore_state(pdev);

}