[PATCH v1 14/18] vfio/mdev: Add mdev available instance checking to the core

Eric Farman
2022-06-02T17:20:20Z

From: Jason Gunthorpe <jgg@nvidia.com>

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_type. Implement it using correct locking, fixing mdpy.

Drivers provide a get_available() callback to set the number of available
instances for their mtypes which is fixed at registration time. The core
provides a standard sysfs attribute to return the available_instances.

Cc: Kirti Wankhede <kwankhede@nvidia.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Tony Krowiak <akrowiak@linux.ibm.com>
Cc: Jason Herne <jjherne@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/7-v3-57c1502c62fd+2190-ccw_mdev_jgg@nvidia.com/
[farman: added Cc: tags]
Signed-off-by: Eric Farman <farman@linux.ibm.com>
---
.../driver-api/vfio-mediated-device.rst | 4 +-
drivers/s390/cio/vfio_ccw_drv.c | 1 -
drivers/s390/cio/vfio_ccw_ops.c | 26 ++++---------
drivers/s390/cio/vfio_ccw_private.h | 2 -
drivers/s390/crypto/vfio_ap_ops.c | 32 ++++------------
drivers/s390/crypto/vfio_ap_private.h | 2 -
drivers/vfio/mdev/mdev_core.c | 11 +++++-
drivers/vfio/mdev/mdev_private.h | 2 +
drivers/vfio/mdev/mdev_sysfs.c | 37 +++++++++++++++++++
include/linux/mdev.h | 2 +
samples/vfio-mdev/mdpy.c | 22 +++--------
11 files changed, 76 insertions(+), 65 deletions(-)

diff --git a/Documentation/driver-api/vfio-mediated-device.rst b/Documentation/driver-api/vfio-mediated-device.rst
index f410a1cd98bb..a4f7f1362fa8 100644
--- a/Documentation/driver-api/vfio-mediated-device.rst
+++ b/Documentation/driver-api/vfio-mediated-device.rst
@@ -106,6 +106,7 @@ structure to represent a mediated device's driver::
int (*probe) (struct mdev_device *dev);
void (*remove) (struct mdev_device *dev);
struct device_driver driver;
+ unsigned int (*get_available)(struct mdev_type *mtype);
};

A mediated bus driver for mdev should use this structure in the function calls
@@ -232,7 +233,8 @@ Directories and files under the sysfs for Each Physical Device
* available_instances

This attribute should show the number of devices of type <type-id> that can be
- created.
+ created. Drivers can supply a get_available() function pointer to have the
+ core code create and maintain this sysfs automatically.

* [device]

diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index e4b285953a45..6dca35f3ceba 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -147,7 +147,6 @@ 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 6793c8b3c58b..60a4855e8ecb 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -66,20 +66,9 @@ static ssize_t name_show(struct mdev_type *mtype,
}
static MDEV_TYPE_ATTR_RO(name);

-static ssize_t available_instances_show(struct mdev_type *mtype,
- struct mdev_type_attribute *attr,
- char *buf)
-{
- struct vfio_ccw_private *private =
- dev_get_drvdata(mtype_get_parent_dev(mtype));
-
- return sprintf(buf, "%d\n", atomic_read(&private->avail));
-}
-static MDEV_TYPE_ATTR_RO(available_instances);

static struct attribute *mdev_types_attrs[] = {
&mdev_type_attr_name.attr,
- &mdev_type_attr_available_instances.attr,
NULL,
};

@@ -101,9 +90,6 @@ 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);
@@ -115,13 +101,12 @@ static int vfio_ccw_mdev_probe(struct mdev_device *mdev)

ret = vfio_register_emulated_iommu_dev(&private->vdev);
if (ret)
- goto err_atomic;
+ goto err_init;
dev_set_drvdata(&mdev->dev, private);
return 0;

-err_atomic:
+err_init:
vfio_uninit_group_dev(&private->vdev);
- atomic_inc(&private->avail);
return ret;
}

@@ -143,7 +128,6 @@ static void vfio_ccw_mdev_remove(struct mdev_device *mdev)
vfio_ccw_fsm_event(private, VFIO_CCW_EVENT_CLOSE);

vfio_uninit_group_dev(&private->vdev);
- atomic_inc(&private->avail);
}

static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
@@ -614,6 +598,11 @@ static void vfio_ccw_mdev_request(struct vfio_device *vdev, unsigned int count)
}
}

+static unsigned int vfio_ccw_get_available(struct mdev_type *mtype)
+{
+ return 1;
+}
+
static const struct vfio_device_ops vfio_ccw_dev_ops = {
.open_device = vfio_ccw_mdev_open_device,
.close_device = vfio_ccw_mdev_close_device,
@@ -631,6 +620,7 @@ struct mdev_driver vfio_ccw_mdev_driver = {
},
.probe = vfio_ccw_mdev_probe,
.remove = vfio_ccw_mdev_remove,
+ .get_available = vfio_ccw_get_available,
};

const struct mdev_parent_ops vfio_ccw_mdev_ops = {
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index 02a4a5edd00c..e568fd6bcf2a 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
* @nb: notifier for vfio events
* @io_region: MMIO region to input/output I/O arguments/results
* @io_mutex: protect against concurrent update of I/O regions
@@ -95,7 +94,6 @@ struct vfio_ccw_private {
struct subchannel *sch;
int state;
struct completion *completion;
- atomic_t avail;
struct notifier_block nb;
struct ccw_io_region *io_region;
struct mutex io_mutex;
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 838b1a3eac8a..4c62ba9c72d8 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -462,14 +462,9 @@ 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);

@@ -492,8 +487,6 @@ 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;
}

@@ -509,7 +502,6 @@ 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 ssize_t name_show(struct mdev_type *mtype,
@@ -520,20 +512,8 @@ static ssize_t name_show(struct mdev_type *mtype,

static MDEV_TYPE_ATTR_RO(name);

-static ssize_t available_instances_show(struct mdev_type *mtype,
- struct mdev_type_attribute *attr,
- char *buf)
-{
- return sprintf(buf, "%d\n",
- atomic_read(&matrix_dev->available_instances));
-}
-
-static MDEV_TYPE_ATTR_RO(available_instances);
-
-
static struct attribute *vfio_ap_mdev_type_attrs[] = {
&mdev_type_attr_name.attr,
- &mdev_type_attr_available_instances.attr,
NULL,
};

@@ -1473,6 +1453,11 @@ static ssize_t vfio_ap_mdev_ioctl(struct vfio_device *vdev,
return ret;
}

+static unsigned int vfio_ap_mdev_get_available(struct mdev_type *mtype)
+{
+ return MAX_ZDEV_ENTRIES_EXT;
+}
+
static const struct vfio_device_ops vfio_ap_matrix_dev_ops = {
.open_device = vfio_ap_mdev_open_device,
.close_device = vfio_ap_mdev_close_device,
@@ -1488,6 +1473,7 @@ 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,
};

static const struct mdev_parent_ops vfio_ap_matrix_ops = {
@@ -1501,8 +1487,6 @@ 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 648fcaf8104a..5c0cbf03074b 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
* @lock: mutex for locking the AP matrix device. This lock will be
@@ -41,7 +40,6 @@
*/
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 c3018e8e6d32..bb27ca0db948 100644
--- a/drivers/vfio/mdev/mdev_core.c
+++ b/drivers/vfio/mdev/mdev_core.c
@@ -25,7 +25,7 @@ static DEFINE_MUTEX(parent_list_lock);
static struct class_compat *mdev_bus_compat_class;

static LIST_HEAD(mdev_list);
-static DEFINE_MUTEX(mdev_list_lock);
+DEFINE_MUTEX(mdev_list_lock);

struct device *mdev_parent_dev(struct mdev_device *mdev)
{
@@ -245,6 +245,7 @@ static void mdev_device_release(struct device *dev)

mutex_lock(&mdev_list_lock);
list_del(&mdev->next);
+ mdev->type->available++;
mutex_unlock(&mdev_list_lock);

dev_dbg(&mdev->dev, "MDEV: destroying\n");
@@ -268,6 +269,14 @@ int mdev_device_create(struct mdev_type *type, const guid_t *uuid)
}
}

+ if (drv && drv->get_available) {
+ if (!type->available) {
+ mutex_unlock(&mdev_list_lock);
+ return -EUSERS;
+ }
+ type->available--;
+ }
+
mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
if (!mdev) {
mutex_unlock(&mdev_list_lock);
diff --git a/drivers/vfio/mdev/mdev_private.h b/drivers/vfio/mdev/mdev_private.h
index afbad7b0a14a..83586b070233 100644
--- a/drivers/vfio/mdev/mdev_private.h
+++ b/drivers/vfio/mdev/mdev_private.h
@@ -29,6 +29,7 @@ struct mdev_type {
struct kobject *devices_kobj;
struct mdev_parent *parent;
struct list_head next;
+ unsigned int available;
unsigned int type_group_id;
};

@@ -38,6 +39,7 @@ struct mdev_type {
container_of(_kobj, struct mdev_type, kobj)

extern struct mdev_driver vfio_mdev_driver;
+extern struct mutex mdev_list_lock;

int parent_create_sysfs_files(struct mdev_parent *parent);
void parent_remove_sysfs_files(struct mdev_parent *parent);
diff --git a/drivers/vfio/mdev/mdev_sysfs.c b/drivers/vfio/mdev/mdev_sysfs.c
index d4b99440d19e..b3129dfc27ef 100644
--- a/drivers/vfio/mdev/mdev_sysfs.c
+++ b/drivers/vfio/mdev/mdev_sysfs.c
@@ -93,8 +93,41 @@ static struct attribute_group mdev_type_std_group = {
.attrs = mdev_types_std_attrs,
};

+/* mdev_type attribute used by drivers that have an get_available() op */
+static ssize_t available_instances_show(struct mdev_type *mtype,
+ struct mdev_type_attribute *attr,
+ char *buf)
+{
+ unsigned int available;
+
+ mutex_lock(&mdev_list_lock);
+ available = mtype->available;
+ mutex_unlock(&mdev_list_lock);
+
+ return sysfs_emit(buf, "%u\n", available);
+}
+static MDEV_TYPE_ATTR_RO(available_instances);
+static umode_t available_instances_is_visible(struct kobject *kobj,
+ struct attribute *attr, int n)
+{
+ struct mdev_type *type = to_mdev_type(kobj);
+
+ if (!type->parent->ops->device_driver->get_available)
+ return 0;
+ return attr->mode;
+}
+static struct attribute *mdev_types_name_attrs[] = {
+ &mdev_type_attr_available_instances.attr,
+ NULL,
+};
+static struct attribute_group mdev_type_available_instances_group = {
+ .attrs = mdev_types_name_attrs,
+ .is_visible = available_instances_is_visible,
+};
+
static const struct attribute_group *mdev_type_groups[] = {
&mdev_type_std_group,
+ &mdev_type_available_instances_group,
NULL,
};

@@ -136,6 +169,10 @@ static struct mdev_type *add_mdev_supported_type(struct mdev_parent *parent,
mdev_get_parent(parent);
type->type_group_id = type_group_id;

+ if (parent->ops->device_driver->get_available)
+ type->available =
+ parent->ops->device_driver->get_available(type);
+
ret = kobject_init_and_add(&type->kobj, &mdev_type_ktype, NULL,
"%s-%s", dev_driver_string(parent->dev),
group->name);
diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index 14655215417b..0ce1bb3dabd0 100644
--- a/include/linux/mdev.h
+++ b/include/linux/mdev.h
@@ -120,12 +120,14 @@ struct mdev_type_attribute {
* @probe: called when new device created
* @remove: called when device removed
* @driver: device driver structure
+ * @get_available: Return the max number of instances that can be created
*
**/
struct mdev_driver {
int (*probe)(struct mdev_device *dev);
void (*remove)(struct mdev_device *dev);
struct device_driver driver;
+ unsigned int (*get_available)(struct mdev_type *mtype);
};

static inline void *mdev_get_drvdata(struct mdev_device *mdev)
diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index 402a7ebe6563..d7da6ed35657 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -84,7 +84,6 @@ static dev_t mdpy_devt;
static struct class *mdpy_class;
static struct cdev mdpy_cdev;
static struct device mdpy_dev;
-static u32 mdpy_count;
static const struct vfio_device_ops mdpy_dev_ops;

/* State of each mdev device */
@@ -225,9 +224,6 @@ 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;
@@ -256,8 +252,6 @@ 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;
@@ -284,8 +278,6 @@ 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,
@@ -662,18 +654,10 @@ static ssize_t description_show(struct mdev_type *mtype,
}
static MDEV_TYPE_ATTR_RO(description);

-static ssize_t available_instances_show(struct mdev_type *mtype,
- struct mdev_type_attribute *attr,
- char *buf)
-{
- return sprintf(buf, "%d\n", max_devices - mdpy_count);
-}
-static MDEV_TYPE_ATTR_RO(available_instances);

static struct attribute *mdev_types_attrs[] = {
&mdev_type_attr_name.attr,
&mdev_type_attr_description.attr,
- &mdev_type_attr_available_instances.attr,
NULL,
};

@@ -706,6 +690,11 @@ static const struct vfio_device_ops mdpy_dev_ops = {
.mmap = mdpy_mmap,
};

+static unsigned int mdpy_get_available(struct mdev_type *mtype)
+{
+ return max_devices;
+}
+
static struct mdev_driver mdpy_driver = {
.driver = {
.name = "mdpy",
@@ -715,6 +704,7 @@ static struct mdev_driver mdpy_driver = {
},
.probe = mdpy_probe,
.remove = mdpy_remove,
+ .get_available = mdpy_get_available,
};

static const struct mdev_parent_ops mdev_fops = {
--
2.32.0