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 e5f21c725326ba689e15de772e09176a718e0f64..7f5402fe857a2e6d2fbc5292b1fd88718c3d49d1 100644 (file)
--- 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 559ca180559283d657852c7d5feae16f2a81685d..6ae4d012d800845bf5cad2b68abefd5bbc4e2164 100644 (file)
--- 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 52caa721ec06c511352771c99822bd10f1f527b4..bd5fb81456af854c0a87a2b27262e72f66a3d04d 100644 (file)
--- 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 8606f5d75188cab10cb72875a6e96f463e87b8ae..2884189f387711ec42d46b917808b5423c0a119e 100644 (file)
--- 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 441dc8dda380bbb021e80ae90bac2a98fca4b86f..2eddd5f34ed34c55e9f0473a8d1c90c0224a2d6f 100644 (file)
--- 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 93f8caf2e5f773f2ecf1314757e02829eb329b04..58f91b3bd670cc4fc88608dad02f9ab7eb24cb76 100644 (file)
--- 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 658b3bf5ed0bfe760adcee26cc7b668300542790..abe3359dd477fc67364084d39141d6018ebad9e0 100644 (file)
--- 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 33674cb5ed5d45d741f73fed760e4bfa500f9e3f..139d05b26f820aed916fe2be175dd67f5379d02c 100644 (file)
--- 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 a7cf59246ddd04c0fd5306b3d3ecf402feae0ab2..946e8cfde6fdd649cb01b8eea63cdc0ae76a5848 100644 (file)
--- 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)