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Commit bc4fba77 authored by Alex Williamson's avatar Alex Williamson
Browse files

vfio-pci: Attempt bus/slot reset on release 



Each time a device is released, mark whether a local reset was
successful or whether a bus/slot reset is needed.  If a reset is
needed and all of the affected devices are bound to vfio-pci and
unused, allow the reset.  This is most useful when the userspace
driver is killed and releases all the devices in an unclean state,
such as when a QEMU VM quits.

Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 61d79256

drivers/vfio/pci/vfio_pci.c

+112 −0
Original line number Diff line number Diff line
@@ -39,6 +39,8 @@ MODULE_PARM_DESC(nointxmask, 


static DEFINE_MUTEX(driver_lock);



static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev);



static int vfio_pci_enable(struct vfio_pci_device *vdev)

{

	struct pci_dev *pdev = vdev->pdev;
@@ -123,6 +125,8 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev) 
		vdev->barmap[bar] = NULL;

	}



	vdev->needs_reset = true;



	/*

	 * If we have saved state, restore it.  If we can reset the device,

	 * even better.  Resetting with current state seems better than
@@ -154,11 +158,15 @@ static void vfio_pci_disable(struct vfio_pci_device *vdev) 
		if (ret)

			pr_warn("%s: Failed to reset device %s (%d)\n",

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

		else

			vdev->needs_reset = false;

	}



	pci_restore_state(pdev);

out:

	pci_disable_device(pdev);



	vfio_pci_try_bus_reset(vdev);

}



static void vfio_pci_release(void *device_data)
@@ -923,6 +931,110 @@ static struct pci_driver vfio_pci_driver = { 
	.err_handler	= &vfio_err_handlers,

};



/*

 * Test whether a reset is necessary and possible.  We mark devices as

 * needs_reset when they are released, but don't have a function-local reset

 * available.  If any of these exist in the affected devices, we want to do

 * a bus/slot reset.  We also need all of the affected devices to be unused,

 * so we abort if any device has a non-zero refcnt.  driver_lock prevents a

 * device from being opened during the scan or unbound from vfio-pci.

 */

static int vfio_pci_test_bus_reset(struct pci_dev *pdev, void *data)

{

	bool *needs_reset = data;

	struct pci_driver *pci_drv = ACCESS_ONCE(pdev->driver);

	int ret = -EBUSY;



	if (pci_drv == &vfio_pci_driver) {

		struct vfio_device *device;

		struct vfio_pci_device *vdev;



		device = vfio_device_get_from_dev(&pdev->dev);

		if (!device)

			return ret;



		vdev = vfio_device_data(device);

		if (vdev) {

			if (vdev->needs_reset)

				*needs_reset = true;



			if (!vdev->refcnt)

				ret = 0;

		}



		vfio_device_put(device);

	}



	/*

	 * TODO: vfio-core considers groups to be viable even if some devices

	 * are attached to known drivers, like pci-stub or pcieport.  We can't

	 * freeze devices from being unbound to those drivers like we can

	 * here though, so it would be racy to test for them.  We also can't

	 * use device_lock() to prevent changes as that would interfere with

	 * PCI-core taking device_lock during bus reset.  For now, we require

	 * devices to be bound to vfio-pci to get a bus/slot reset on release.

	 */



	return ret;

}



/* Clear needs_reset on all affected devices after successful bus/slot reset */

static int vfio_pci_clear_needs_reset(struct pci_dev *pdev, void *data)

{

	struct pci_driver *pci_drv = ACCESS_ONCE(pdev->driver);



	if (pci_drv == &vfio_pci_driver) {

		struct vfio_device *device;

		struct vfio_pci_device *vdev;



		device = vfio_device_get_from_dev(&pdev->dev);

		if (!device)

			return 0;



		vdev = vfio_device_data(device);

		if (vdev)

			vdev->needs_reset = false;



		vfio_device_put(device);

	}



	return 0;

}



/*

 * Attempt to do a bus/slot reset if there are devices affected by a reset for

 * this device that are needs_reset and all of the affected devices are unused

 * (!refcnt).  Callers of this function are required to hold driver_lock such

 * that devices can not be unbound from vfio-pci or opened by a user while we

 * test for and perform a bus/slot reset.

 */

static void vfio_pci_try_bus_reset(struct vfio_pci_device *vdev)

{

	bool needs_reset = false, slot = false;

	int ret;



	if (!pci_probe_reset_slot(vdev->pdev->slot))

		slot = true;

	else if (pci_probe_reset_bus(vdev->pdev->bus))

		return;



	if (vfio_pci_for_each_slot_or_bus(vdev->pdev,

					  vfio_pci_test_bus_reset,

					  &needs_reset, slot) || !needs_reset)

		return;



	if (slot)

		ret = pci_try_reset_slot(vdev->pdev->slot);

	else

		ret = pci_try_reset_bus(vdev->pdev->bus);



	if (ret)

		return;



	vfio_pci_for_each_slot_or_bus(vdev->pdev,

				      vfio_pci_clear_needs_reset, NULL, slot);

}



static void __exit vfio_pci_cleanup(void)

{

	pci_unregister_driver(&vfio_pci_driver);

drivers/vfio/pci/vfio_pci_private.h

+1 −0
Original line number Diff line number Diff line
@@ -54,6 +54,7 @@ struct vfio_pci_device { 
	bool			extended_caps;

	bool			bardirty;

	bool			has_vga;

	bool			needs_reset;

	struct pci_saved_state	*pci_saved_state;

	int			refcnt;

	struct eventfd_ctx	*err_trigger;