Commit a15ac665 authored by Eric Farman's avatar Eric Farman Committed by Alex Williamson
Browse files

vfio-mdev: Wire in a request handler for mdev parent 



While performing some destructive tests with vfio-ccw, where the
paths to a device are forcible removed and thus the device itself
is unreachable, it is rather easy to end up in an endless loop in
vfio_del_group_dev() due to the lack of a request callback for the
associated device.

In this example, one MDEV (77c) is used by a guest, while another
(77b) is not. The symptom is that the iommu is detached from the
mdev for 77b, but not 77c, until that guest is shutdown:

    [  238.794867] vfio_ccw 0.0.077b: MDEV: Unregistering
    [  238.794996] vfio_mdev 11f2d2bc-4083-431d-a023-eff72715c4f0: Removing from iommu group 2
    [  238.795001] vfio_mdev 11f2d2bc-4083-431d-a023-eff72715c4f0: MDEV: detaching iommu
    [  238.795036] vfio_ccw 0.0.077c: MDEV: Unregistering
    ...silence...

Let's wire in the request call back to the mdev device, so that a
device being physically removed from the host can be (gracefully?)
handled by the parent device at the time the device is removed.

Add a message when registering the device if a driver doesn't
provide this callback, so a clue is given that this same loop
may be encountered in a similar situation, and a message when
this occurs instead of the awkward silence noted above.

Signed-off-by: default avatarEric Farman <farman@linux.ibm.com>
Reviewed-by: default avatarCornelia Huck <cohuck@redhat.com>
Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent d22f9a6c

drivers/vfio/mdev/mdev_core.c

+4 −0
Original line number Diff line number Diff line
@@ -154,6 +154,10 @@ int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops) 
	if (!dev)

		return -EINVAL;



	/* Not mandatory, but its absence could be a problem */

	if (!ops->request)

		dev_info(dev, "Driver cannot be asked to release device\n");



	mutex_lock(&parent_list_lock);



	/* Check for duplicate */

drivers/vfio/mdev/vfio_mdev.c

+13 −0
Original line number Diff line number Diff line
@@ -98,6 +98,18 @@ static int vfio_mdev_mmap(void *device_data, struct vm_area_struct *vma) 
	return parent->ops->mmap(mdev, vma);

}



static void vfio_mdev_request(void *device_data, unsigned int count)

{

	struct mdev_device *mdev = device_data;

	struct mdev_parent *parent = mdev->parent;



	if (parent->ops->request)

		parent->ops->request(mdev, count);

	else if (count == 0)

		dev_notice(mdev_dev(mdev),

			   "No mdev vendor driver request callback support, blocked until released by user\n");

}



static const struct vfio_device_ops vfio_mdev_dev_ops = {

	.name		= "vfio-mdev",

	.open		= vfio_mdev_open,
@@ -106,6 +118,7 @@ static const struct vfio_device_ops vfio_mdev_dev_ops = { 
	.read		= vfio_mdev_read,

	.write		= vfio_mdev_write,

	.mmap		= vfio_mdev_mmap,

	.request	= vfio_mdev_request,

};



static int vfio_mdev_probe(struct device *dev)

include/linux/mdev.h

+4 −0
Original line number Diff line number Diff line
@@ -72,6 +72,9 @@ struct device *mdev_get_iommu_device(struct device *dev); 
 * @mmap:		mmap callback

 *			@mdev: mediated device structure

 *			@vma: vma structure

 * @request:		request callback to release device

 *			@mdev: mediated device structure

 *			@count: request sequence number

 * Parent device that support mediated device should be registered with mdev

 * module with mdev_parent_ops structure.

 **/
@@ -92,6 +95,7 @@ struct mdev_parent_ops { 
	long	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,

			 unsigned long arg);

	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);

	void	(*request)(struct mdev_device *mdev, unsigned int count);

};



/* interface for exporting mdev supported type attributes */

CRA Git | Maintained and supported by SUSTech CRA and CCSE