vfio-pci: Avoid deadlock on remove (d24cdbfd) · Commits · 戴 / test

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:

Alex Williamson <alex.williamson@redhat.com>

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);
		}

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