vfio/mdev: add mdev available instance checking to the core
Many of the mdev drivers use a simple counter for keeping track of the
available instances. Move this code to the core code and store the counter
in the mdev_parent. Implement it using correct locking, fixing mdpy.
Drivers just provide the value in the mdev_driver at registration time
and the core code takes care of maintaining it and exposing the value in
sysfs.
[hch: count instances per-parent instead of per-type, use an atomic_t
to avoid taking mdev_list_lock in the show method]
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Link: https://lore.kernel.org/r/20220923092652.100656-15-hch@lst.de
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index e5f21c7..7f5402f 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -141,7 +141,6 @@ static struct vfio_ccw_private *vfio_ccw_alloc_private(struct subchannel *sch)
INIT_LIST_HEAD(&private->crw);
INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo);
INIT_WORK(&private->crw_work, vfio_ccw_crw_todo);
- atomic_set(&private->avail, 1);
private->cp.guest_cp = kcalloc(CCWCHAIN_LEN_MAX, sizeof(struct ccw1),
GFP_KERNEL);
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index 559ca18..6ae4d01 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -44,13 +44,6 @@ static void vfio_ccw_dma_unmap(struct vfio_device *vdev, u64 iova, u64 length)
vfio_ccw_mdev_reset(private);
}
-static unsigned int vfio_ccw_get_available(struct mdev_type *mtype)
-{
- struct vfio_ccw_private *private = dev_get_drvdata(mtype->parent->dev);
-
- return atomic_read(&private->avail);
-}
-
static int vfio_ccw_mdev_init_dev(struct vfio_device *vdev)
{
struct vfio_ccw_private *private =
@@ -68,9 +61,6 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
if (private->state == VFIO_CCW_STATE_NOT_OPER)
return -ENODEV;
- if (atomic_dec_if_positive(&private->avail) < 0)
- return -EPERM;
-
ret = vfio_init_device(&private->vdev, &mdev->dev, &vfio_ccw_dev_ops);
if (ret)
return ret;
@@ -88,7 +78,6 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
err_put_vdev:
vfio_put_device(&private->vdev);
- atomic_inc(&private->avail);
return ret;
}
@@ -130,8 +119,6 @@ static void vfio_ccw_mdev_remove(struct mdev_device *mdev)
* cycle.
*/
wait_for_completion(&private->release_comp);
-
- atomic_inc(&private->avail);
}
static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
@@ -605,6 +592,7 @@ static const struct vfio_device_ops vfio_ccw_dev_ops = {
struct mdev_driver vfio_ccw_mdev_driver = {
.device_api = VFIO_DEVICE_API_CCW_STRING,
+ .max_instances = 1,
.driver = {
.name = "vfio_ccw_mdev",
.owner = THIS_MODULE,
@@ -612,5 +600,4 @@ struct mdev_driver vfio_ccw_mdev_driver = {
},
.probe = vfio_ccw_mdev_probe,
.remove = vfio_ccw_mdev_remove,
- .get_available = vfio_ccw_get_available,
};
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index 52caa72..bd5fb81 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -73,7 +73,6 @@ struct vfio_ccw_crw {
* @sch: pointer to the subchannel
* @state: internal state of the device
* @completion: synchronization helper of the I/O completion
- * @avail: available for creating a mediated device
* @io_region: MMIO region to input/output I/O arguments/results
* @io_mutex: protect against concurrent update of I/O regions
* @region: additional regions for other subchannel operations
@@ -97,7 +96,6 @@ struct vfio_ccw_private {
struct subchannel *sch;
int state;
struct completion *completion;
- atomic_t avail;
struct ccw_io_region *io_region;
struct mutex io_mutex;
struct vfio_ccw_region *region;
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 8606f5d..2884189 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -689,9 +689,6 @@ static int vfio_ap_mdev_init_dev(struct vfio_device *vdev)
struct ap_matrix_mdev *matrix_mdev =
container_of(vdev, struct ap_matrix_mdev, vdev);
- if ((atomic_dec_if_positive(&matrix_dev->available_instances) < 0))
- return -EPERM;
-
matrix_mdev->mdev = to_mdev_device(vdev->dev);
vfio_ap_matrix_init(&matrix_dev->info, &matrix_mdev->matrix);
matrix_mdev->pqap_hook = handle_pqap;
@@ -770,7 +767,6 @@ static void vfio_ap_mdev_unlink_fr_queues(struct ap_matrix_mdev *matrix_mdev)
static void vfio_ap_mdev_release_dev(struct vfio_device *vdev)
{
- atomic_inc(&matrix_dev->available_instances);
vfio_free_device(vdev);
}
@@ -790,11 +786,6 @@ static void vfio_ap_mdev_remove(struct mdev_device *mdev)
vfio_put_device(&matrix_mdev->vdev);
}
-static unsigned int vfio_ap_mdev_get_available(struct mdev_type *mtype)
-{
- return atomic_read(&matrix_dev->available_instances);
-}
-
#define MDEV_SHARING_ERR "Userspace may not re-assign queue %02lx.%04lx " \
"already assigned to %s"
@@ -1772,6 +1763,7 @@ static const struct vfio_device_ops vfio_ap_matrix_dev_ops = {
static struct mdev_driver vfio_ap_matrix_driver = {
.device_api = VFIO_DEVICE_API_AP_STRING,
+ .max_instances = MAX_ZDEV_ENTRIES_EXT,
.driver = {
.name = "vfio_ap_mdev",
.owner = THIS_MODULE,
@@ -1780,15 +1772,12 @@ static struct mdev_driver vfio_ap_matrix_driver = {
},
.probe = vfio_ap_mdev_probe,
.remove = vfio_ap_mdev_remove,
- .get_available = vfio_ap_mdev_get_available,
};
int vfio_ap_mdev_register(void)
{
int ret;
- atomic_set(&matrix_dev->available_instances, MAX_ZDEV_ENTRIES_EXT);
-
ret = mdev_register_driver(&vfio_ap_matrix_driver);
if (ret)
return ret;
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 441dc8d..2eddd5f 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -29,7 +29,6 @@
* struct ap_matrix_dev - Contains the data for the matrix device.
*
* @device: generic device structure associated with the AP matrix device
- * @available_instances: number of mediated matrix devices that can be created
* @info: the struct containing the output from the PQAP(QCI) instruction
* @mdev_list: the list of mediated matrix devices created
* @mdevs_lock: mutex for locking the AP matrix device. This lock will be
@@ -46,7 +45,6 @@
*/
struct ap_matrix_dev {
struct device device;
- atomic_t available_instances;
struct ap_config_info info;
struct list_head mdev_list;
struct mutex mdevs_lock; /* serializes access to each ap_matrix_mdev */
diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
index 93f8caf..58f91b3 100644
--- a/drivers/vfio/mdev/mdev_core.c
+++ b/drivers/vfio/mdev/mdev_core.c
@@ -70,6 +70,7 @@ int mdev_register_parent(struct mdev_parent *parent, struct device *dev,
parent->mdev_driver = mdev_driver;
parent->types = types;
parent->nr_types = nr_types;
+ atomic_set(&parent->available_instances, mdev_driver->max_instances);
if (!mdev_bus_compat_class) {
mdev_bus_compat_class = class_compat_register("mdev_bus");
@@ -115,14 +116,17 @@ EXPORT_SYMBOL(mdev_unregister_parent);
static void mdev_device_release(struct device *dev)
{
struct mdev_device *mdev = to_mdev_device(dev);
-
- /* Pairs with the get in mdev_device_create() */
- kobject_put(&mdev->type->kobj);
+ struct mdev_parent *parent = mdev->type->parent;
mutex_lock(&mdev_list_lock);
list_del(&mdev->next);
+ if (!parent->mdev_driver->get_available)
+ atomic_inc(&parent->available_instances);
mutex_unlock(&mdev_list_lock);
+ /* Pairs with the get in mdev_device_create() */
+ kobject_put(&mdev->type->kobj);
+
dev_dbg(&mdev->dev, "MDEV: destroying\n");
kfree(mdev);
}
@@ -144,6 +148,18 @@ int mdev_device_create(struct mdev_type *type, const guid_t *uuid)
}
}
+ if (!drv->get_available) {
+ /*
+ * Note: that non-atomic read and dec is fine here because
+ * all modifications are under mdev_list_lock.
+ */
+ if (!atomic_read(&parent->available_instances)) {
+ mutex_unlock(&mdev_list_lock);
+ return -EUSERS;
+ }
+ atomic_dec(&parent->available_instances);
+ }
+
mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
if (!mdev) {
mutex_unlock(&mdev_list_lock);
diff --git a/drivers/vfio/mdev/mdev_sysfs.c b/drivers/vfio/mdev/mdev_sysfs.c
index 658b3bf..abe3359 100644
--- a/drivers/vfio/mdev/mdev_sysfs.c
+++ b/drivers/vfio/mdev/mdev_sysfs.c
@@ -108,7 +108,10 @@ static ssize_t available_instances_show(struct mdev_type *mtype,
{
struct mdev_driver *drv = mtype->parent->mdev_driver;
- return sysfs_emit(buf, "%u\n", drv->get_available(mtype));
+ if (drv->get_available)
+ return sysfs_emit(buf, "%u\n", drv->get_available(mtype));
+ return sysfs_emit(buf, "%u\n",
+ atomic_read(&mtype->parent->available_instances));
}
static MDEV_TYPE_ATTR_RO(available_instances);
diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index 33674cb..139d05b 100644
--- a/include/linux/mdev.h
+++ b/include/linux/mdev.h
@@ -45,6 +45,7 @@ struct mdev_parent {
struct rw_semaphore unreg_sem;
struct mdev_type **types;
unsigned int nr_types;
+ atomic_t available_instances;
};
static inline struct mdev_device *to_mdev_device(struct device *dev)
@@ -55,6 +56,7 @@ static inline struct mdev_device *to_mdev_device(struct device *dev)
/**
* struct mdev_driver - Mediated device driver
* @device_api: string to return for the device_api sysfs
+ * @max_instances: maximum number of instances supported (optional)
* @probe: called when new device created
* @remove: called when device removed
* @get_available: Return the max number of instances that can be created
@@ -63,6 +65,7 @@ static inline struct mdev_device *to_mdev_device(struct device *dev)
**/
struct mdev_driver {
const char *device_api;
+ unsigned int max_instances;
int (*probe)(struct mdev_device *dev);
void (*remove)(struct mdev_device *dev);
unsigned int (*get_available)(struct mdev_type *mtype);
diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index a7cf592..946e8cf 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -42,11 +42,6 @@
MODULE_LICENSE("GPL v2");
-static int max_devices = 4;
-module_param_named(count, max_devices, int, 0444);
-MODULE_PARM_DESC(count, "number of " MDPY_NAME " devices");
-
-
#define MDPY_TYPE_1 "vga"
#define MDPY_TYPE_2 "xga"
#define MDPY_TYPE_3 "hd"
@@ -93,7 +88,6 @@ static struct class *mdpy_class;
static struct cdev mdpy_cdev;
static struct device mdpy_dev;
static struct mdev_parent mdpy_parent;
-static u32 mdpy_count;
static const struct vfio_device_ops mdpy_dev_ops;
/* State of each mdev device */
@@ -235,9 +229,6 @@ static int mdpy_init_dev(struct vfio_device *vdev)
u32 fbsize;
int ret = -ENOMEM;
- if (mdpy_count >= max_devices)
- return ret;
-
mdev_state->vconfig = kzalloc(MDPY_CONFIG_SPACE_SIZE, GFP_KERNEL);
if (!mdev_state->vconfig)
return ret;
@@ -257,8 +248,6 @@ static int mdpy_init_dev(struct vfio_device *vdev)
dev_info(vdev->dev, "%s: %s (%dx%d)\n", __func__, type->type.pretty_name,
type->width, type->height);
-
- mdpy_count++;
return 0;
out_vconfig:
@@ -292,7 +281,6 @@ static void mdpy_release_dev(struct vfio_device *vdev)
struct mdev_state *mdev_state =
container_of(vdev, struct mdev_state, vdev);
- mdpy_count--;
vfree(mdev_state->memblk);
kfree(mdev_state->vconfig);
vfio_free_device(vdev);
@@ -669,11 +657,6 @@ static ssize_t mdpy_show_description(struct mdev_type *mtype, char *buf)
type->width, type->height);
}
-static unsigned int mdpy_get_available(struct mdev_type *mtype)
-{
- return max_devices - mdpy_count;
-}
-
static const struct vfio_device_ops mdpy_dev_ops = {
.init = mdpy_init_dev,
.release = mdpy_release_dev,
@@ -685,6 +668,7 @@ static const struct vfio_device_ops mdpy_dev_ops = {
static struct mdev_driver mdpy_driver = {
.device_api = VFIO_DEVICE_API_PCI_STRING,
+ .max_instances = 4,
.driver = {
.name = "mdpy",
.owner = THIS_MODULE,
@@ -693,7 +677,6 @@ static struct mdev_driver mdpy_driver = {
},
.probe = mdpy_probe,
.remove = mdpy_remove,
- .get_available = mdpy_get_available,
.show_description = mdpy_show_description,
};
@@ -770,5 +753,8 @@ static void __exit mdpy_dev_exit(void)
mdpy_class = NULL;
}
+module_param_named(count, mdpy_driver.max_instances, int, 0444);
+MODULE_PARM_DESC(count, "number of " MDPY_NAME " devices");
+
module_init(mdpy_dev_init)
module_exit(mdpy_dev_exit)
