[PATCH 13/13] vfio/mdev: add mdev available instance checking to the core

Christoph Hellwig
2022-06-28T05:17:43Z

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.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
[count instances per-parent instead of per-type]
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/s390/cio/vfio_ccw_drv.c | 1 -
drivers/s390/cio/vfio_ccw_ops.c | 14 +-------------
drivers/s390/cio/vfio_ccw_private.h | 2 --
drivers/s390/crypto/vfio_ap_ops.c | 21 +++------------------
drivers/s390/crypto/vfio_ap_private.h | 2 --
drivers/vfio/mdev/mdev_core.c | 12 ++++++++++++
include/linux/mdev.h | 3 +++
samples/vfio-mdev/mdpy.c | 23 ++++-------------------
8 files changed, 23 insertions(+), 55 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 750d0315f1f5b..449c76b29a3b5 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -149,7 +149,6 @@ 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 94cc62b808088..b89ac599a9087 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -70,13 +70,6 @@ static int vfio_ccw_mdev_notifier(struct notifier_block *nb,
return NOTIFY_DONE;
}

-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_probe(struct mdev_device *mdev)
{
struct vfio_ccw_private *private = dev_get_drvdata(mdev->dev.parent);
@@ -85,9 +78,6 @@ 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;
-
memset(&private->vdev, 0, sizeof(private->vdev));
vfio_init_group_dev(&private->vdev, &mdev->dev,
&vfio_ccw_dev_ops);
@@ -108,7 +98,6 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)

err_atomic:
vfio_uninit_group_dev(&private->vdev);
- atomic_inc(&private->avail);
private->mdev = NULL;
private->state = VFIO_CCW_STATE_IDLE;
return ret;
@@ -135,7 +124,6 @@ static void vfio_ccw_mdev_remove(struct mdev_device *mdev)
vfio_uninit_group_dev(&private->vdev);
cp_free(&private->cp);
private->mdev = NULL;
- atomic_inc(&private->avail);
}

static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
@@ -613,6 +601,7 @@ 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,
@@ -620,7 +609,6 @@ struct mdev_driver vfio_ccw_mdev_driver = {
},
.probe = vfio_ccw_mdev_probe,
.remove = vfio_ccw_mdev_remove,
- .get_available = vfio_ccw_get_available,
};

int vfio_ccw_mdev_reg(struct subchannel *sch)
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index b7163bac8cc75..9be5baed0cb7f 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -72,7 +72,6 @@ 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
* @mdev: pointer to the mediated device
* @nb: notifier for vfio events
* @io_region: MMIO region to input/output I/O arguments/results
@@ -96,7 +95,6 @@ struct vfio_ccw_private {
struct subchannel *sch;
int state;
struct completion *completion;
- atomic_t avail;
struct mdev_device *mdev;
struct notifier_block nb;
struct ccw_io_region *io_region;
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 5e6cc43413117..3d1108f1b7556 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -461,14 +461,9 @@ static int vfio_ap_mdev_probe(struct mdev_device *mdev)
struct ap_matrix_mdev *matrix_mdev;
int ret;

- if ((atomic_dec_if_positive(&matrix_dev->available_instances) < 0))
- return -EPERM;
-
matrix_mdev = kzalloc(sizeof(*matrix_mdev), GFP_KERNEL);
- if (!matrix_mdev) {
- ret = -ENOMEM;
- goto err_dec_available;
- }
+ if (!matrix_mdev)
+ return -ENOMEM;
vfio_init_group_dev(&matrix_mdev->vdev, &mdev->dev,
&vfio_ap_matrix_dev_ops);

@@ -491,8 +486,6 @@ static int vfio_ap_mdev_probe(struct mdev_device *mdev)
mutex_unlock(&matrix_dev->lock);
vfio_uninit_group_dev(&matrix_mdev->vdev);
kfree(matrix_mdev);
-err_dec_available:
- atomic_inc(&matrix_dev->available_instances);
return ret;
}

@@ -508,12 +501,6 @@ static void vfio_ap_mdev_remove(struct mdev_device *mdev)
mutex_unlock(&matrix_dev->lock);
vfio_uninit_group_dev(&matrix_mdev->vdev);
kfree(matrix_mdev);
- atomic_inc(&matrix_dev->available_instances);
-}
-
-static unsigned int vfio_ap_mdev_get_available(struct mdev_type *mtype)
-{
- return atomic_read(&matrix_dev->available_instances);
}

struct vfio_ap_queue_reserved {
@@ -1427,6 +1414,7 @@ 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,
@@ -1435,15 +1423,12 @@ 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 5dc5050d03791..b808b343b771f 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -28,7 +28,6 @@
* 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
* @lock: mutex for locking the AP matrix device. This lock will be
@@ -40,7 +39,6 @@
*/
struct ap_matrix_dev {
struct device device;
- atomic_t available_instances;
struct ap_config_info info;
struct list_head mdev_list;
struct mutex lock;
diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
index 93f8caf2e5f77..775efbfed1f35 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;
+ parent->available_instances = mdev_driver->max_instances;

if (!mdev_bus_compat_class) {
mdev_bus_compat_class = class_compat_register("mdev_bus");
@@ -115,12 +116,15 @@ EXPORT_SYMBOL(mdev_unregister_parent);
static void mdev_device_release(struct device *dev)
{
struct mdev_device *mdev = to_mdev_device(dev);
+ struct mdev_parent *parent = mdev->type->parent;

/* Pairs with the get in mdev_device_create() */
kobject_put(&mdev->type->kobj);

mutex_lock(&mdev_list_lock);
list_del(&mdev->next);
+ if (!parent->mdev_driver->get_available)
+ parent->available_instances++;
mutex_unlock(&mdev_list_lock);

dev_dbg(&mdev->dev, "MDEV: destroying\n");
@@ -144,6 +148,14 @@ int mdev_device_create(struct mdev_type *type, const guid_t *uuid)
}
}

+ if (!drv->get_available) {
+ if (!parent->available_instances) {
+ mutex_unlock(&mdev_list_lock);
+ return -EUSERS;
+ }
+ parent->available_instances--;
+ }
+
mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
if (!mdev) {
mutex_unlock(&mdev_list_lock);
diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index 968494a9f72e3..9ea470e61d7d9 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;
+ unsigned int 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 250b7ea2df2e4..7f7ac5491407e 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 */
@@ -234,9 +228,6 @@ static int mdpy_probe(struct mdev_device *mdev)
u32 fbsize;
int ret;

- if (mdpy_count >= max_devices)
- return -ENOMEM;
-
mdev_state = kzalloc(sizeof(struct mdev_state), GFP_KERNEL);
if (mdev_state == NULL)
return -ENOMEM;
@@ -265,8 +256,6 @@ static int mdpy_probe(struct mdev_device *mdev)
mdpy_create_config_space(mdev_state);
mdpy_reset(mdev_state);

- mdpy_count++;
-
ret = vfio_register_emulated_iommu_dev(&mdev_state->vdev);
if (ret)
goto err_mem;
@@ -293,8 +282,6 @@ static void mdpy_remove(struct mdev_device *mdev)
kfree(mdev_state->vconfig);
vfio_uninit_group_dev(&mdev_state->vdev);
kfree(mdev_state);
-
- mdpy_count--;
}

static ssize_t mdpy_read(struct vfio_device *vdev, char __user *buf,
@@ -658,11 +645,6 @@ 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 = {
.read = mdpy_read,
.write = mdpy_write,
@@ -672,6 +654,7 @@ 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,
@@ -680,7 +663,6 @@ static struct mdev_driver mdpy_driver = {
},
.probe = mdpy_probe,
.remove = mdpy_remove,
- .get_available = mdpy_get_available,
.show_description = mdpy_show_description,
};

@@ -757,5 +739,8 @@ 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)
--
2.30.2