Re: [PATCH RFC v3 13/14] dmaengine: idxd: add char driver to expose submission portal to userland

[Dave Jiang <dave.jiang@intel.com>]

On 1/7/20 10:45 AM, Dave Jiang wrote:
> 
> 
> On 12/26/19 10:58 PM, Vinod Koul wrote:
>> On 17-12-19, 16:34, Dave Jiang wrote:
>>> Create a char device region that will allow acquisition of user portals in
>>> order to allow applications to submit DMA operations. A char device will be
>>> created per work queue that gets exposed. The workqueue type "user"
>>> is used to mark a work queue for user char device. For example if the
>>> workqueue 0 of DSA device 0 is marked for char device, then a device node
>>> of /dev/dsa/wq0.0 will be created.
>>
>> do we really want to create a device specific interface..? why not move
>> it to dmaengine core and create a dmaengine device for userland to
>> submit dma operations?
> 
> I'm keeping an eye on the uacce framework [1] progress. If that goes
> upstream then there's probably not any reason for dmaengine to export
> that. Otherwise then yes that would be reasonable. Are you thinking that
> the uacce guys should consider doing that for dmaengine instead?
> 
> The char device export in idxd driver is a bridge solution until we
> bottom out on whichever interface to provide the generic framework.

Oops forgot to provide URL

[1]: https://lkml.org/lkml/2019/12/15/332

> 
>>
>>>
>>> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
>>> ---
>>>    drivers/dma/idxd/Makefile |    2
>>>    drivers/dma/idxd/cdev.c   |  302 +++++++++++++++++++++++++++++++++++++++++++++
>>>    drivers/dma/idxd/device.c |    2
>>>    drivers/dma/idxd/idxd.h   |   38 ++++++
>>>    drivers/dma/idxd/init.c   |   10 +
>>>    drivers/dma/idxd/irq.c    |   18 +++
>>>    drivers/dma/idxd/submit.c |    4 -
>>>    drivers/dma/idxd/sysfs.c  |   52 +++++++-
>>>    8 files changed, 423 insertions(+), 5 deletions(-)
>>>    create mode 100644 drivers/dma/idxd/cdev.c
>>>
>>> diff --git a/drivers/dma/idxd/Makefile b/drivers/dma/idxd/Makefile
>>> index a036ba0e77d2..8978b898d777 100644
>>> --- a/drivers/dma/idxd/Makefile
>>> +++ b/drivers/dma/idxd/Makefile
>>> @@ -1,2 +1,2 @@
>>>    obj-$(CONFIG_INTEL_IDXD) += idxd.o
>>> -idxd-y := init.o irq.o device.o sysfs.o submit.o dma.o
>>> +idxd-y := init.o irq.o device.o sysfs.o submit.o dma.o cdev.o
>>> diff --git a/drivers/dma/idxd/cdev.c b/drivers/dma/idxd/cdev.c
>>> new file mode 100644
>>> index 000000000000..1d7347825b95
>>> --- /dev/null
>>> +++ b/drivers/dma/idxd/cdev.c
>>> @@ -0,0 +1,302 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/* Copyright(c) 2019 Intel Corporation. All rights rsvd. */
>>> +#include <linux/init.h>
>>> +#include <linux/kernel.h>
>>> +#include <linux/module.h>
>>> +#include <linux/pci.h>
>>> +#include <linux/device.h>
>>> +#include <linux/sched/task.h>
>>> +#include <linux/intel-svm.h>
>>> +#include <linux/io-64-nonatomic-lo-hi.h>
>>> +#include <linux/cdev.h>
>>> +#include <linux/fs.h>
>>> +#include <linux/poll.h>
>>> +#include <uapi/linux/idxd.h>
>>> +#include "registers.h"
>>> +#include "idxd.h"
>>> +
>>> +struct idxd_cdev_context {
>>> +	const char *name;
>>> +	dev_t devt;
>>> +	struct ida minor_ida;
>>> +};
>>> +
>>> +/*
>>> + * ictx is an array based off of accelerator types. enum idxd_type
>>> + * is used as index
>>> + */
>>> +static struct idxd_cdev_context ictx[IDXD_TYPE_MAX] = {
>>> +	{ .name = "dsa" },
>>> +};
>>> +
>>> +struct idxd_user_context {
>>> +	struct idxd_wq *wq;
>>> +	struct task_struct *task;
>>> +	unsigned int flags;
>>> +};
>>> +
>>> +enum idxd_cdev_cleanup {
>>> +	CDEV_NORMAL = 0,
>>> +	CDEV_FAILED,
>>> +};
>>> +
>>> +static void idxd_cdev_dev_release(struct device *dev)
>>> +{
>>> +	dev_dbg(dev, "releasing cdev device\n");
>>> +	kfree(dev);
>>> +}
>>> +
>>> +static struct device_type idxd_cdev_device_type = {
>>> +	.name = "idxd_cdev",
>>> +	.release = idxd_cdev_dev_release,
>>> +};
>>> +
>>> +static inline struct idxd_cdev *inode_idxd_cdev(struct inode *inode)
>>> +{
>>> +	struct cdev *cdev = inode->i_cdev;
>>> +
>>> +	return container_of(cdev, struct idxd_cdev, cdev);
>>> +}
>>> +
>>> +static inline struct idxd_wq *idxd_cdev_wq(struct idxd_cdev *idxd_cdev)
>>> +{
>>> +	return container_of(idxd_cdev, struct idxd_wq, idxd_cdev);
>>> +}
>>> +
>>> +static inline struct idxd_wq *inode_wq(struct inode *inode)
>>> +{
>>> +	return idxd_cdev_wq(inode_idxd_cdev(inode));
>>> +}
>>> +
>>> +static int idxd_cdev_open(struct inode *inode, struct file *filp)
>>> +{
>>> +	struct idxd_user_context *ctx;
>>> +	struct idxd_device *idxd;
>>> +	struct idxd_wq *wq;
>>> +	struct device *dev;
>>> +	struct idxd_cdev *idxd_cdev;
>>> +
>>> +	wq = inode_wq(inode);
>>> +	idxd = wq->idxd;
>>> +	dev = &idxd->pdev->dev;
>>> +	idxd_cdev = &wq->idxd_cdev;
>>> +
>>> +	dev_dbg(dev, "%s called\n", __func__);
>>> +
>>> +	if (idxd_wq_refcount(wq) > 1 && wq_dedicated(wq))
>>> +		return -EBUSY;
>>> +
>>> +	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
>>> +	if (!ctx)
>>> +		return -ENOMEM;
>>> +
>>> +	ctx->wq = wq;
>>> +	filp->private_data = ctx;
>>> +	idxd_wq_get(wq);
>>> +	return 0;
>>> +}
>>> +
>>> +static int idxd_cdev_release(struct inode *node, struct file *filep)
>>> +{
>>> +	struct idxd_user_context *ctx = filep->private_data;
>>> +	struct idxd_wq *wq = ctx->wq;
>>> +	struct idxd_device *idxd = wq->idxd;
>>> +	struct device *dev = &idxd->pdev->dev;
>>> +
>>> +	dev_dbg(dev, "%s called\n", __func__);
>>> +	filep->private_data = NULL;
>>> +
>>> +	kfree(ctx);
>>> +	idxd_wq_put(wq);
>>> +	return 0;
>>> +}
>>> +
>>> +static int check_vma(struct idxd_wq *wq, struct vm_area_struct *vma,
>>> +		     const char *func)
>>> +{
>>> +	struct device *dev = &wq->idxd->pdev->dev;
>>> +
>>> +	if ((vma->vm_end - vma->vm_start) > PAGE_SIZE) {
>>> +		dev_info_ratelimited(dev,
>>> +				     "%s: %s: mapping too large: %lu\n",
>>> +				     current->comm, func,
>>> +				     vma->vm_end - vma->vm_start);
>>> +		return -EINVAL;
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int idxd_cdev_mmap(struct file *filp, struct vm_area_struct *vma)
>>> +{
>>> +	struct idxd_user_context *ctx = filp->private_data;
>>> +	struct idxd_wq *wq = ctx->wq;
>>> +	struct idxd_device *idxd = wq->idxd;
>>> +	struct pci_dev *pdev = idxd->pdev;
>>> +	phys_addr_t base = pci_resource_start(pdev, IDXD_WQ_BAR);
>>> +	unsigned long pfn;
>>> +	int rc;
>>> +
>>> +	dev_dbg(&pdev->dev, "%s called\n", __func__);
>>> +	rc = check_vma(wq, vma, __func__);
>>> +
>>> +	vma->vm_flags |= VM_DONTCOPY;
>>> +	pfn = (base + idxd_get_wq_portal_full_offset(wq->id,
>>> +				IDXD_PORTAL_LIMITED)) >> PAGE_SHIFT;
>>> +	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>>> +	vma->vm_private_data = ctx;
>>> +
>>> +	return io_remap_pfn_range(vma, vma->vm_start, pfn, PAGE_SIZE,
>>> +			vma->vm_page_prot);
>>> +}
>>> +
>>> +static __poll_t idxd_cdev_poll(struct file *filp,
>>> +			       struct poll_table_struct *wait)
>>> +{
>>> +	struct idxd_user_context *ctx = filp->private_data;
>>> +	struct idxd_wq *wq = ctx->wq;
>>> +	struct idxd_device *idxd = wq->idxd;
>>> +	struct idxd_cdev *idxd_cdev = &wq->idxd_cdev;
>>> +	unsigned long flags;
>>> +	__poll_t out = 0;
>>> +
>>> +	poll_wait(filp, &idxd_cdev->err_queue, wait);
>>> +	spin_lock_irqsave(&idxd->dev_lock, flags);
>>> +	if (idxd->sw_err.valid)
>>> +		out = EPOLLIN | EPOLLRDNORM;
>>> +	spin_unlock_irqrestore(&idxd->dev_lock, flags);
>>> +
>>> +	return out;
>>> +}
>>> +
>>> +static const struct file_operations idxd_cdev_fops = {
>>> +	.owner = THIS_MODULE,
>>> +	.open = idxd_cdev_open,
>>> +	.release = idxd_cdev_release,
>>> +	.mmap = idxd_cdev_mmap,
>>> +	.poll = idxd_cdev_poll,
>>> +};
>>> +
>>> +int idxd_cdev_get_major(struct idxd_device *idxd)
>>> +{
>>> +	return MAJOR(ictx[idxd->type].devt);
>>> +}
>>> +
>>> +static int idxd_wq_cdev_dev_setup(struct idxd_wq *wq)
>>> +{
>>> +	struct idxd_device *idxd = wq->idxd;
>>> +	struct idxd_cdev *idxd_cdev = &wq->idxd_cdev;
>>> +	struct idxd_cdev_context *cdev_ctx;
>>> +	struct device *dev;
>>> +	int minor, rc;
>>> +
>>> +	idxd_cdev->dev = kzalloc(sizeof(*idxd_cdev->dev), GFP_KERNEL);
>>> +	if (!idxd_cdev->dev)
>>> +		return -ENOMEM;
>>> +
>>> +	dev = idxd_cdev->dev;
>>> +	dev->parent = &idxd->pdev->dev;
>>> +	dev_set_name(dev, "%s/wq%u.%u", idxd_get_dev_name(idxd),
>>> +		     idxd->id, wq->id);
>>> +	dev->bus = idxd_get_bus_type(idxd);
>>> +
>>> +	cdev_ctx = &ictx[wq->idxd->type];
>>> +	minor = ida_simple_get(&cdev_ctx->minor_ida, 0, MINORMASK, GFP_KERNEL);
>>> +	if (minor < 0) {
>>> +		rc = minor;
>>> +		goto ida_err;
>>> +	}
>>> +
>>> +	dev->devt = MKDEV(MAJOR(cdev_ctx->devt), minor);
>>> +	dev->type = &idxd_cdev_device_type;
>>> +	rc = device_register(dev);
>>> +	if (rc < 0) {
>>> +		dev_err(&idxd->pdev->dev, "device register failed\n");
>>> +		put_device(dev);
>>> +		goto dev_reg_err;
>>> +	}
>>> +	idxd_cdev->minor = minor;
>>> +
>>> +	return 0;
>>> +
>>> + dev_reg_err:
>>> +	ida_simple_remove(&cdev_ctx->minor_ida, MINOR(dev->devt));
>>> + ida_err:
>>> +	kfree(dev);
>>> +	idxd_cdev->dev = NULL;
>>> +	return rc;
>>> +}
>>> +
>>> +static void idxd_wq_cdev_cleanup(struct idxd_wq *wq,
>>> +				 enum idxd_cdev_cleanup cdev_state)
>>> +{
>>> +	struct idxd_cdev *idxd_cdev = &wq->idxd_cdev;
>>> +	struct idxd_cdev_context *cdev_ctx;
>>> +
>>> +	cdev_ctx = &ictx[wq->idxd->type];
>>> +	if (cdev_state == CDEV_NORMAL)
>>> +		cdev_del(&idxd_cdev->cdev);
>>> +	device_unregister(idxd_cdev->dev);
>>> +	/*
>>> +	 * The device_type->release() will be called on the device and free
>>> +	 * the allocated struct device. We can just forget it.
>>> +	 */
>>> +	ida_simple_remove(&cdev_ctx->minor_ida, idxd_cdev->minor);
>>> +	idxd_cdev->dev = NULL;
>>> +	idxd_cdev->minor = -1;
>>> +}
>>> +
>>> +int idxd_wq_add_cdev(struct idxd_wq *wq)
>>> +{
>>> +	struct idxd_cdev *idxd_cdev = &wq->idxd_cdev;
>>> +	struct cdev *cdev = &idxd_cdev->cdev;
>>> +	struct device *dev;
>>> +	int rc;
>>> +
>>> +	rc = idxd_wq_cdev_dev_setup(wq);
>>> +	if (rc < 0)
>>> +		return rc;
>>> +
>>> +	dev = idxd_cdev->dev;
>>> +	cdev_init(cdev, &idxd_cdev_fops);
>>> +	cdev_set_parent(cdev, &dev->kobj);
>>> +	rc = cdev_add(cdev, dev->devt, 1);
>>> +	if (rc) {
>>> +		dev_dbg(&wq->idxd->pdev->dev, "cdev_add failed: %d\n", rc);
>>> +		idxd_wq_cdev_cleanup(wq, CDEV_FAILED);
>>> +		return rc;
>>> +	}
>>> +
>>> +	init_waitqueue_head(&idxd_cdev->err_queue);
>>> +	return 0;
>>> +}
>>> +
>>> +void idxd_wq_del_cdev(struct idxd_wq *wq)
>>> +{
>>> +	idxd_wq_cdev_cleanup(wq, CDEV_NORMAL);
>>> +}
>>> +
>>> +int idxd_cdev_register(void)
>>> +{
>>> +	int rc, i;
>>> +
>>> +	for (i = 0; i < IDXD_TYPE_MAX; i++) {
>>> +		ida_init(&ictx[i].minor_ida);
>>> +		rc = alloc_chrdev_region(&ictx[i].devt, 0, MINORMASK,
>>> +					 ictx[i].name);
>>> +		if (rc)
>>> +			return rc;
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +void idxd_cdev_remove(void)
>>> +{
>>> +	int i;
>>> +
>>> +	for (i = 0; i < IDXD_TYPE_MAX; i++) {
>>> +		unregister_chrdev_region(ictx[i].devt, MINORMASK);
>>> +		ida_destroy(&ictx[i].minor_ida);
>>> +	}
>>> +}
>>> diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
>>> index 49638d3a2151..fd33e2985e95 100644
>>> --- a/drivers/dma/idxd/device.c
>>> +++ b/drivers/dma/idxd/device.c
>>> @@ -545,7 +545,7 @@ static int idxd_wq_config_write(struct idxd_wq *wq)
>>>    	wq->wqcfg.wq_thresh = wq->threshold;
>>>    
>>>    	/* byte 8-11 */
>>> -	wq->wqcfg.priv = 1; /* kernel, therefore priv */
>>> +	wq->wqcfg.priv = !!(wq->type == IDXD_WQT_KERNEL);
>>>    	wq->wqcfg.mode = 1;
>>>    
>>>    	wq->wqcfg.priority = wq->priority;
>>> diff --git a/drivers/dma/idxd/idxd.h b/drivers/dma/idxd/idxd.h
>>> index fc1634e689cf..23bf12ad0af4 100644
>>> --- a/drivers/dma/idxd/idxd.h
>>> +++ b/drivers/dma/idxd/idxd.h
>>> @@ -7,6 +7,7 @@
>>>    #include <linux/dmaengine.h>
>>>    #include <linux/percpu-rwsem.h>
>>>    #include <linux/wait.h>
>>> +#include <linux/cdev.h>
>>>    #include "registers.h"
>>>    
>>>    #define IDXD_DRIVER_VERSION	"1.00"
>>> @@ -63,6 +64,14 @@ enum idxd_wq_flag {
>>>    enum idxd_wq_type {
>>>    	IDXD_WQT_NONE = 0,
>>>    	IDXD_WQT_KERNEL,
>>> +	IDXD_WQT_USER,
>>> +};
>>> +
>>> +struct idxd_cdev {
>>> +	struct cdev cdev;
>>> +	struct device *dev;
>>> +	int minor;
>>> +	struct wait_queue_head err_queue;
>>>    };
>>>    
>>>    #define IDXD_ALLOCATED_BATCH_SIZE	128U
>>> @@ -72,6 +81,7 @@ enum idxd_wq_type {
>>>    struct idxd_wq {
>>>    	void __iomem *dportal;
>>>    	struct device conf_dev;
>>> +	struct idxd_cdev idxd_cdev;
>>>    	struct idxd_device *idxd;
>>>    	int id;
>>>    	enum idxd_wq_type type;
>>> @@ -139,6 +149,7 @@ struct idxd_device {
>>>    	enum idxd_device_state state;
>>>    	unsigned long flags;
>>>    	int id;
>>> +	int major;
>>>    
>>>    	struct pci_dev *pdev;
>>>    	void __iomem *reg_base;
>>> @@ -192,11 +203,29 @@ struct idxd_desc {
>>>    #define confdev_to_idxd(dev) container_of(dev, struct idxd_device, conf_dev)
>>>    #define confdev_to_wq(dev) container_of(dev, struct idxd_wq, conf_dev)
>>>    
>>> +extern struct bus_type dsa_bus_type;
>>> +
>>>    static inline bool wq_dedicated(struct idxd_wq *wq)
>>>    {
>>>    	return test_bit(WQ_FLAG_DEDICATED, &wq->flags);
>>>    }
>>>    
>>> +enum idxd_portal_prot {
>>> +	IDXD_PORTAL_UNLIMITED = 0,
>>> +	IDXD_PORTAL_LIMITED,
>>> +};
>>> +
>>> +static inline int idxd_get_wq_portal_offset(enum idxd_portal_prot prot)
>>> +{
>>> +	return prot * 0x1000;
>>> +}
>>> +
>>> +static inline int idxd_get_wq_portal_full_offset(int wq_id,
>>> +						 enum idxd_portal_prot prot)
>>> +{
>>> +	return ((wq_id * 4) << PAGE_SHIFT) + idxd_get_wq_portal_offset(prot);
>>> +}
>>> +
>>>    static inline void idxd_set_type(struct idxd_device *idxd)
>>>    {
>>>    	struct pci_dev *pdev = idxd->pdev;
>>> @@ -229,6 +258,7 @@ int idxd_setup_sysfs(struct idxd_device *idxd);
>>>    void idxd_cleanup_sysfs(struct idxd_device *idxd);
>>>    int idxd_register_driver(void);
>>>    void idxd_unregister_driver(void);
>>> +struct bus_type *idxd_get_bus_type(struct idxd_device *idxd);
>>>    
>>>    /* device interrupt control */
>>>    irqreturn_t idxd_irq_handler(int vec, void *data);
>>> @@ -267,4 +297,12 @@ void idxd_unregister_dma_device(struct idxd_device *idxd);
>>>    int idxd_register_dma_channel(struct idxd_wq *wq);
>>>    void idxd_unregister_dma_channel(struct idxd_wq *wq);
>>>    void idxd_parse_completion_status(u8 status, enum dmaengine_tx_result *res);
>>> +
>>> +/* cdev */
>>> +int idxd_cdev_register(void);
>>> +void idxd_cdev_remove(void);
>>> +int idxd_cdev_get_major(struct idxd_device *idxd);
>>> +int idxd_wq_add_cdev(struct idxd_wq *wq);
>>> +void idxd_wq_del_cdev(struct idxd_wq *wq);
>>> +
>>>    #endif
>>> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
>>> index b2e887508078..b247ef57f5c1 100644
>>> --- a/drivers/dma/idxd/init.c
>>> +++ b/drivers/dma/idxd/init.c
>>> @@ -188,6 +188,7 @@ static int idxd_setup_internals(struct idxd_device *idxd)
>>>    		mutex_init(&wq->wq_lock);
>>>    		atomic_set(&wq->dq_count, 0);
>>>    		init_waitqueue_head(&wq->submit_waitq);
>>> +		wq->idxd_cdev.minor = -1;
>>>    		rc = percpu_init_rwsem(&wq->submit_lock);
>>>    		if (rc < 0) {
>>>    			idxd_wqs_free_lock(idxd);
>>> @@ -321,6 +322,8 @@ static int idxd_probe(struct idxd_device *idxd)
>>>    		goto err_idr_fail;
>>>    	}
>>>    
>>> +	idxd->major = idxd_cdev_get_major(idxd);
>>> +
>>>    	dev_dbg(dev, "IDXD device %d probed successfully\n", idxd->id);
>>>    	return 0;
>>>    
>>> @@ -519,6 +522,10 @@ static int __init idxd_init_module(void)
>>>    	if (err < 0)
>>>    		goto err_idxd_driver_register;
>>>    
>>> +	err = idxd_cdev_register();
>>> +	if (err)
>>> +		goto err_cdev_register;
>>> +
>>>    	err = pci_register_driver(&idxd_pci_driver);
>>>    	if (err)
>>>    		goto err_pci_register;
>>> @@ -526,6 +533,8 @@ static int __init idxd_init_module(void)
>>>    	return 0;
>>>    
>>>    err_pci_register:
>>> +	idxd_cdev_remove();
>>> +err_cdev_register:
>>>    	idxd_unregister_driver();
>>>    err_idxd_driver_register:
>>>    	idxd_unregister_bus_type();
>>> @@ -536,6 +545,7 @@ module_init(idxd_init_module);
>>>    static void __exit idxd_exit_module(void)
>>>    {
>>>    	pci_unregister_driver(&idxd_pci_driver);
>>> +	idxd_cdev_remove();
>>>    	idxd_unregister_bus_type();
>>>    }
>>>    module_exit(idxd_exit_module);
>>> diff --git a/drivers/dma/idxd/irq.c b/drivers/dma/idxd/irq.c
>>> index b4adeb2817d1..442f21eeb0fb 100644
>>> --- a/drivers/dma/idxd/irq.c
>>> +++ b/drivers/dma/idxd/irq.c
>>> @@ -89,6 +89,24 @@ irqreturn_t idxd_misc_thread(int vec, void *data)
>>>    			idxd->sw_err.bits[i] = ioread64(idxd->reg_base +
>>>    					IDXD_SWERR_OFFSET + i * sizeof(u64));
>>>    		iowrite64(IDXD_SWERR_ACK, idxd->reg_base + IDXD_SWERR_OFFSET);
>>> +
>>> +		if (idxd->sw_err.valid && idxd->sw_err.wq_idx_valid) {
>>> +			int id = idxd->sw_err.wq_idx;
>>> +			struct idxd_wq *wq = &idxd->wqs[id];
>>> +
>>> +			if (wq->type == IDXD_WQT_USER)
>>> +				wake_up_interruptible(&wq->idxd_cdev.err_queue);
>>> +		} else {
>>> +			int i;
>>> +
>>> +			for (i = 0; i < idxd->max_wqs; i++) {
>>> +				struct idxd_wq *wq = &idxd->wqs[i];
>>> +
>>> +				if (wq->type == IDXD_WQT_USER)
>>> +					wake_up_interruptible(&wq->idxd_cdev.err_queue);
>>> +			}
>>> +		}
>>> +
>>>    		spin_unlock_bh(&idxd->dev_lock);
>>>    		val |= IDXD_INTC_ERR;
>>>    
>>> diff --git a/drivers/dma/idxd/submit.c b/drivers/dma/idxd/submit.c
>>> index f7baa1bbb0c7..0e6dea34edc9 100644
>>> --- a/drivers/dma/idxd/submit.c
>>> +++ b/drivers/dma/idxd/submit.c
>>> @@ -71,17 +71,19 @@ static int idxd_submit_desc(struct idxd_wq *wq, struct idxd_desc *desc,
>>>    {
>>>    	struct idxd_device *idxd = wq->idxd;
>>>    	int vec = desc->hw->int_handle;
>>> +	void __iomem *portal;
>>>    
>>>    	if (idxd->state != IDXD_DEV_ENABLED)
>>>    		return -EIO;
>>>    
>>> +	portal = wq->dportal + idxd_get_wq_portal_offset(IDXD_PORTAL_UNLIMITED);
>>>    	/*
>>>    	 * The wmb() flushes writes to coherent DMA data before possibly
>>>    	 * triggering a DMA read. The wmb() is necessary even on UP because
>>>    	 * the recipient is a device.
>>>    	 */
>>>    	wmb();
>>> -	iosubmit_cmds512(wq->dportal, desc->hw, 1);
>>> +	iosubmit_cmds512(portal, desc->hw, 1);
>>>    
>>>    	/*
>>>    	 * Pending the descriptor to the lockless list for the irq_entry
>>> diff --git a/drivers/dma/idxd/sysfs.c b/drivers/dma/idxd/sysfs.c
>>> index bcbd6020c8ee..4d0480ec97f7 100644
>>> --- a/drivers/dma/idxd/sysfs.c
>>> +++ b/drivers/dma/idxd/sysfs.c
>>> @@ -13,6 +13,7 @@
>>>    static char *idxd_wq_type_names[] = {
>>>    	[IDXD_WQT_NONE]		= "none",
>>>    	[IDXD_WQT_KERNEL]	= "kernel",
>>> +	[IDXD_WQT_USER]		= "user",
>>>    };
>>>    
>>>    static void idxd_conf_device_release(struct device *dev)
>>> @@ -63,6 +64,11 @@ static inline bool is_idxd_wq_dmaengine(struct idxd_wq *wq)
>>>    	return false;
>>>    }
>>>    
>>> +static inline bool is_idxd_wq_cdev(struct idxd_wq *wq)
>>> +{
>>> +	return wq->type == IDXD_WQT_USER ? true : false;
>>> +}
>>> +
>>>    static int idxd_config_bus_match(struct device *dev,
>>>    				 struct device_driver *drv)
>>>    {
>>> @@ -109,6 +115,9 @@ static int idxd_config_bus_probe(struct device *dev)
>>>    			return -EBUSY;
>>>    		}
>>>    
>>> +		if (!try_module_get(THIS_MODULE))
>>> +			return -ENXIO;
>>> +
>>>    		spin_lock_irqsave(&idxd->dev_lock, flags);
>>>    
>>>    		/* Perform IDXD configuration and enabling */
>>> @@ -216,6 +225,13 @@ static int idxd_config_bus_probe(struct device *dev)
>>>    				mutex_unlock(&wq->wq_lock);
>>>    				return rc;
>>>    			}
>>> +		} else if (is_idxd_wq_cdev(wq)) {
>>> +			rc = idxd_wq_add_cdev(wq);
>>> +			if (rc < 0) {
>>> +				dev_dbg(dev, "Cdev creation failed\n");
>>> +				mutex_unlock(&wq->wq_lock);
>>> +				return rc;
>>> +			}
>>>    		}
>>>    
>>>    		mutex_unlock(&wq->wq_lock);
>>> @@ -241,6 +257,8 @@ static void disable_wq(struct idxd_wq *wq)
>>>    
>>>    	if (is_idxd_wq_dmaengine(wq))
>>>    		idxd_unregister_dma_channel(wq);
>>> +	else if (is_idxd_wq_cdev(wq))
>>> +		idxd_wq_del_cdev(wq);
>>>    
>>>    	if (idxd_wq_refcount(wq))
>>>    		dev_warn(dev, "Clients has claim on wq %d: %d\n",
>>> @@ -295,10 +313,12 @@ static int idxd_config_bus_remove(struct device *dev)
>>>    		spin_lock_irqsave(&idxd->dev_lock, flags);
>>>    		rc = idxd_device_disable(idxd);
>>>    		spin_unlock_irqrestore(&idxd->dev_lock, flags);
>>> +		module_put(THIS_MODULE);
>>>    		if (rc < 0)
>>>    			dev_warn(dev, "Device disable failed\n");
>>>    		else
>>>    			dev_info(dev, "Device %s disabled\n", dev_name(dev));
>>> +
>>>    	}
>>>    
>>>    	return 0;
>>> @@ -309,7 +329,7 @@ static void idxd_config_bus_shutdown(struct device *dev)
>>>    	dev_dbg(dev, "%s called\n", __func__);
>>>    }
>>>    
>>> -static struct bus_type dsa_bus_type = {
>>> +struct bus_type dsa_bus_type = {
>>>    	.name = "dsa",
>>>    	.match = idxd_config_bus_match,
>>>    	.probe = idxd_config_bus_probe,
>>> @@ -334,7 +354,7 @@ static struct idxd_device_driver *idxd_drvs[] = {
>>>    	&dsa_drv
>>>    };
>>>    
>>> -static struct bus_type *idxd_get_bus_type(struct idxd_device *idxd)
>>> +struct bus_type *idxd_get_bus_type(struct idxd_device *idxd)
>>>    {
>>>    	return idxd_bus_types[idxd->type];
>>>    }
>>> @@ -956,6 +976,9 @@ static ssize_t wq_type_show(struct device *dev,
>>>    	case IDXD_WQT_KERNEL:
>>>    		return sprintf(buf, "%s\n",
>>>    			       idxd_wq_type_names[IDXD_WQT_KERNEL]);
>>> +	case IDXD_WQT_USER:
>>> +		return sprintf(buf, "%s\n",
>>> +			       idxd_wq_type_names[IDXD_WQT_USER]);
>>>    	case IDXD_WQT_NONE:
>>>    	default:
>>>    		return sprintf(buf, "%s\n",
>>> @@ -978,6 +1001,8 @@ static ssize_t wq_type_store(struct device *dev,
>>>    	old_type = wq->type;
>>>    	if (sysfs_streq(buf, idxd_wq_type_names[IDXD_WQT_KERNEL]))
>>>    		wq->type = IDXD_WQT_KERNEL;
>>> +	else if (sysfs_streq(buf, idxd_wq_type_names[IDXD_WQT_USER]))
>>> +		wq->type = IDXD_WQT_USER;
>>>    	else
>>>    		wq->type = IDXD_WQT_NONE;
>>>    
>>> @@ -1020,6 +1045,17 @@ static ssize_t wq_name_store(struct device *dev,
>>>    static struct device_attribute dev_attr_wq_name =
>>>    		__ATTR(name, 0644, wq_name_show, wq_name_store);
>>>    
>>> +static ssize_t wq_cdev_minor_show(struct device *dev,
>>> +				  struct device_attribute *attr, char *buf)
>>> +{
>>> +	struct idxd_wq *wq = container_of(dev, struct idxd_wq, conf_dev);
>>> +
>>> +	return sprintf(buf, "%d\n", wq->idxd_cdev.minor);
>>> +}
>>> +
>>> +static struct device_attribute dev_attr_wq_cdev_minor =
>>> +		__ATTR(cdev_minor, 0444, wq_cdev_minor_show, NULL);
>>> +
>>>    static struct attribute *idxd_wq_attributes[] = {
>>>    	&dev_attr_wq_clients.attr,
>>>    	&dev_attr_wq_state.attr,
>>> @@ -1029,6 +1065,7 @@ static struct attribute *idxd_wq_attributes[] = {
>>>    	&dev_attr_wq_priority.attr,
>>>    	&dev_attr_wq_type.attr,
>>>    	&dev_attr_wq_name.attr,
>>> +	&dev_attr_wq_cdev_minor.attr,
>>>    	NULL,
>>>    };
>>>    
>>> @@ -1242,6 +1279,16 @@ static ssize_t token_limit_store(struct device *dev,
>>>    }
>>>    static DEVICE_ATTR_RW(token_limit);
>>>    
>>> +static ssize_t cdev_major_show(struct device *dev,
>>> +			       struct device_attribute *attr, char *buf)
>>> +{
>>> +	struct idxd_device *idxd =
>>> +		container_of(dev, struct idxd_device, conf_dev);
>>> +
>>> +	return sprintf(buf, "%u\n", idxd->major);
>>> +}
>>> +static DEVICE_ATTR_RO(cdev_major);
>>> +
>>>    static struct attribute *idxd_device_attributes[] = {
>>>    	&dev_attr_max_groups.attr,
>>>    	&dev_attr_max_work_queues.attr,
>>> @@ -1257,6 +1304,7 @@ static struct attribute *idxd_device_attributes[] = {
>>>    	&dev_attr_errors.attr,
>>>    	&dev_attr_max_tokens.attr,
>>>    	&dev_attr_token_limit.attr,
>>> +	&dev_attr_cdev_major.attr,
>>>    	NULL,
>>>    };
>>>    
>>