dmaengine: idxd: add char driver to expose submission portal to userland

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.

Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/157965026985.73301.976523230037106742.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

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

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);
+	}
+}

drivers/dma/idxd/device.c

@@ -539,7 +539,7 @@ 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;