Commit 97d0a687 authored by Alex Williamson's avatar Alex Williamson
Browse files

vfio/mtty: Enforce available_instances 

The sample mtty mdev driver doesn't actually enforce the number of
device instances it claims are available.  Implement this properly.

Link: https://lore.kernel.org/r/162465624894.3338367.12935940647049917981.stgit@omen


Reviewed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Reviewed-by: default avatarCornelia Huck <cohuck@redhat.com>
Reviewed by: Kirti Wankhede <kwankhede@nvidia.com>
Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 0dd1b7fc

samples/vfio-mdev/mtty.c

+16 −6
Original line number Diff line number Diff line
@@ -144,7 +144,7 @@ struct mdev_state { 
	int nr_ports;

};



static atomic_t mdev_used_ports;

static atomic_t mdev_avail_ports = ATOMIC_INIT(MAX_MTTYS);



static const struct file_operations vd_fops = {

	.owner          = THIS_MODULE,
@@ -707,11 +707,20 @@ static int mtty_probe(struct mdev_device *mdev) 
{

	struct mdev_state *mdev_state;

	int nr_ports = mdev_get_type_group_id(mdev) + 1;

	int avail_ports = atomic_read(&mdev_avail_ports);

	int ret;



	do {

		if (avail_ports < nr_ports)

			return -ENOSPC;

	} while (!atomic_try_cmpxchg(&mdev_avail_ports,

				     &avail_ports, avail_ports - nr_ports));



	mdev_state = kzalloc(sizeof(struct mdev_state), GFP_KERNEL);

	if (mdev_state == NULL)

	if (mdev_state == NULL) {

		atomic_add(nr_ports, &mdev_avail_ports);

		return -ENOMEM;

	}



	vfio_init_group_dev(&mdev_state->vdev, &mdev->dev, &mtty_dev_ops);
@@ -724,6 +733,7 @@ static int mtty_probe(struct mdev_device *mdev) 


	if (mdev_state->vconfig == NULL) {

		kfree(mdev_state);

		atomic_add(nr_ports, &mdev_avail_ports);

		return -ENOMEM;

	}
@@ -735,9 +745,9 @@ static int mtty_probe(struct mdev_device *mdev) 
	ret = vfio_register_group_dev(&mdev_state->vdev);

	if (ret) {

		kfree(mdev_state);

		atomic_add(nr_ports, &mdev_avail_ports);

		return ret;

	}

	atomic_add(mdev_state->nr_ports, &mdev_used_ports);



	dev_set_drvdata(&mdev->dev, mdev_state);

	return 0;
@@ -746,12 +756,13 @@ static int mtty_probe(struct mdev_device *mdev) 
static void mtty_remove(struct mdev_device *mdev)

{

	struct mdev_state *mdev_state = dev_get_drvdata(&mdev->dev);

	int nr_ports = mdev_state->nr_ports;



	atomic_sub(mdev_state->nr_ports, &mdev_used_ports);

	vfio_unregister_group_dev(&mdev_state->vdev);



	kfree(mdev_state->vconfig);

	kfree(mdev_state);

	atomic_add(nr_ports, &mdev_avail_ports);

}



static int mtty_reset(struct mdev_state *mdev_state)
@@ -1271,8 +1282,7 @@ static ssize_t available_instances_show(struct mdev_type *mtype, 
{

	unsigned int ports = mtype_get_type_group_id(mtype) + 1;



	return sprintf(buf, "%d\n",

		       (MAX_MTTYS - atomic_read(&mdev_used_ports)) / ports);

	return sprintf(buf, "%d\n", atomic_read(&mdev_avail_ports) / ports);

}



static MDEV_TYPE_ATTR_RO(available_instances);