Re: [PATCH 14/15] vfio/mdev: add mdev available instance checking to the core

Kirti Wankhede
2022-07-06T13:37:36Z

Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>

On 7/6/2022 1:12 PM, Christoph Hellwig wrote:
> 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>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> ---
> 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 | 18 +++++++++++++++---
> include/linux/mdev.h | 3 +++
> samples/vfio-mdev/mdpy.c | 23 ++++-------------------
> 8 files changed, 26 insertions(+), 58 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 6f6a0f2695059..c05d80add7be2 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 edeec11c56560..69ed88fdaf383 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..9bc897235c492 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");
> @@ -115,14 +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)
> + 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 +148,14 @@ 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 dc38ad2b07883..641ed18a61247 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)