Re: [PATCH v7 01/14] dmaengine: idxd: add wq driver name support for accel-config user tool

[Fenghua Yu <fenghua.yu@intel.com>]

Hi, Tom,

On 7/10/23 12:06, Tom Zanussi wrote:
> From: Dave Jiang <dave.jiang@intel.com>
> 
> With the possibility of multiple wq drivers that can be bound to the wq,
> the user config tool accel-config needs a way to know which wq driver to
> bind to the wq. Introduce per wq driver_name sysfs attribute where the user
> can indicate the driver to be bound to the wq. This allows accel-config to
> just bind to the driver using wq->driver_name.
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
>   .../ABI/stable/sysfs-driver-dma-idxd          |  6 ++++
>   drivers/dma/idxd/cdev.c                       |  7 +++++
>   drivers/dma/idxd/dma.c                        |  6 ++++
>   drivers/dma/idxd/idxd.h                       |  9 ++++++
>   drivers/dma/idxd/sysfs.c                      | 28 +++++++++++++++++++
>   include/uapi/linux/idxd.h                     |  1 +
>   6 files changed, 57 insertions(+)
> 
> diff --git a/Documentation/ABI/stable/sysfs-driver-dma-idxd b/Documentation/ABI/stable/sysfs-driver-dma-idxd
> index 534b7a3d59fc..0e577209bee2 100644
> --- a/Documentation/ABI/stable/sysfs-driver-dma-idxd
> +++ b/Documentation/ABI/stable/sysfs-driver-dma-idxd
> @@ -270,6 +270,12 @@ Description:	Shows the operation capability bits displayed in bitmap format
>   		correlates to the operations allowed. It's visible only
>   		on platforms that support the capability.
>   
> +What:		/sys/bus/dsa/devices/wq<m>.<n>/driver_name
> +Date:		Mar 27, 2023
> +KernelVersion:	6.6.0
> +Contact:	dmaengine@vger.kernel.org
> +Description:	Name of driver to be bounded to the wq.
> +
>   What:           /sys/bus/dsa/devices/engine<m>.<n>/group_id
>   Date:           Oct 25, 2019
>   KernelVersion:  5.6.0
> diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
> index ecbf67c2ad2b..b1ecfb71d95e 100644
> --- a/drivers/dma/idxd/cdev.c
> +++ b/drivers/dma/idxd/cdev.c
> @@ -510,6 +510,7 @@ void idxd_wq_del_cdev(struct idxd_wq *wq)
>   
>   static int idxd_user_drv_probe(struct idxd_dev *idxd_dev)
>   {
> +	struct device *dev = &idxd_dev->conf_dev;
>   	struct idxd_wq *wq = idxd_dev_to_wq(idxd_dev);
>   	struct idxd_device *idxd = wq->idxd;
>   	int rc;
> @@ -537,6 +538,12 @@ static int idxd_user_drv_probe(struct idxd_dev *idxd_dev)
>   
>   	mutex_lock(&wq->wq_lock);
>   
> +	if (!idxd_wq_driver_name_match(wq, dev)) {
> +		idxd->cmd_status = IDXD_SCMD_WQ_NO_DRV_NAME;
> +		rc = -ENODEV;
> +		goto wq_err;
> +	}
> +
>   	wq->wq = create_workqueue(dev_name(wq_confdev(wq)));
>   	if (!wq->wq) {
>   		rc = -ENOMEM;
> diff --git a/drivers/dma/idxd/dma.c b/drivers/dma/idxd/dma.c
> index eb35ca313684..8bb7e7ff8d6a 100644
> --- a/drivers/dma/idxd/dma.c
> +++ b/drivers/dma/idxd/dma.c
> @@ -305,6 +305,12 @@ static int idxd_dmaengine_drv_probe(struct idxd_dev *idxd_dev)
>   		return -ENXIO;
>   
>   	mutex_lock(&wq->wq_lock);
> +	if (!idxd_wq_driver_name_match(wq, dev)) {
> +		idxd->cmd_status = IDXD_SCMD_WQ_NO_DRV_NAME;
> +		rc = -ENODEV;
> +		goto err;
> +	}
> +
>   	wq->type = IDXD_WQT_KERNEL;
>   
>   	rc = drv_enable_wq(wq);
> diff --git a/drivers/dma/idxd/idxd.h b/drivers/dma/idxd/idxd.h
> index 5428a2e1b1ec..c62c78e1c9fa 100644
> --- a/drivers/dma/idxd/idxd.h
> +++ b/drivers/dma/idxd/idxd.h
> @@ -159,6 +159,8 @@ struct idxd_cdev {
>   	int minor;
>   };
>   
> +#define DRIVER_NAME_SIZE		128
> +
>   #define IDXD_ALLOCATED_BATCH_SIZE	128U
>   #define WQ_NAME_SIZE   1024
>   #define WQ_TYPE_SIZE   10
> @@ -227,6 +229,8 @@ struct idxd_wq {
>   	/* Lock to protect upasid_xa access. */
>   	struct mutex uc_lock;
>   	struct xarray upasid_xa;
> +
> +	char driver_name[DRIVER_NAME_SIZE + 1];
>   };
>   
>   struct idxd_engine {
> @@ -637,6 +641,11 @@ static inline void idxd_wqcfg_set_max_batch_shift(int idxd_type, union wqcfg *wq
>   		wqcfg->max_batch_shift = max_batch_shift;
>   }
>   
> +static inline int idxd_wq_driver_name_match(struct idxd_wq *wq, struct device *dev)
> +{
> +	return (strncmp(wq->driver_name, dev->driver->name, strlen(dev->driver->name)) == 0);
> +}
> +
>   int __must_check __idxd_driver_register(struct idxd_device_driver *idxd_drv,
>   					struct module *module, const char *mod_name);
>   #define idxd_driver_register(driver) \
> diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
> index 293739ac5596..6caad044f506 100644
> --- a/drivers/dma/idxd/sysfs.c
> +++ b/drivers/dma/idxd/sysfs.c
> @@ -1266,6 +1266,33 @@ static ssize_t wq_op_config_store(struct device *dev, struct device_attribute *a
>   static struct device_attribute dev_attr_wq_op_config =
>   		__ATTR(op_config, 0644, wq_op_config_show, wq_op_config_store);
>   
> +static ssize_t wq_driver_name_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct idxd_wq *wq = confdev_to_wq(dev);
> +
> +	return sysfs_emit(buf, "%s\n", wq->driver_name);
> +}
> +
> +static ssize_t wq_driver_name_store(struct device *dev, struct device_attribute *attr,
> +				    const char *buf, size_t count)
> +{
> +	struct idxd_wq *wq = confdev_to_wq(dev);
> +
> +	if (wq->state != IDXD_WQ_DISABLED)
> +		return -EPERM;
> +
> +	if (strlen(buf) > DRIVER_NAME_SIZE || strlen(buf) == 0)
> +		return -EINVAL;
> +
> +	memset(wq->driver_name, 0, DRIVER_NAME_SIZE + 1);
> +	strncpy(wq->driver_name, buf, DRIVER_NAME_SIZE);
> +	strreplace(wq->name, '\n', '\0');

If user inputs "dmaengine    " (with the trailing white spaces), the 
trailing white spaces will be copied to wq->driver_name. Later driver 
name match will always fail.

A better way is using strim() to remove the trailing white spaces before 
copying the buffer to wq->driver_name. So wq->driver_name is "dmaengine" 
(without the trailing white spaces).

Thanks.

-Fenghua