[RFC 2/4] vduse: Introduce VDUSE - vDPA Device in Userspace

[Xie Yongji <xieyongji@bytedance.com>]

This VDUSE driver enables implementing vDPA devices in userspace.
Both control path and data path of vDPA devices will be able to
be handled in userspace.

In the control path, the VDUSE driver will make use of message
mechnism to forward the actions (get/set features, get/st status,
get/set config space and set virtqueue states) from virtio-vdpa
driver to userspace. Userspace can use read()/write() to receive/reply
to those control messages.

In the data path, the VDUSE driver implements a MMU-based
on-chip IOMMU driver which supports both direct mapping and
indirect mapping with bounce buffer. Userspace can access those
iova space via mmap(). Besides, eventfd mechnism is used to
trigger interrupts and forward virtqueue kicks.

Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
---
 drivers/vdpa/Kconfig                 |    8 +
 drivers/vdpa/Makefile                |    1 +
 drivers/vdpa/vdpa_user/Makefile      |    5 +
 drivers/vdpa/vdpa_user/eventfd.c     |  221 ++++++
 drivers/vdpa/vdpa_user/eventfd.h     |   48 ++
 drivers/vdpa/vdpa_user/iova_domain.c |  413 +++++++++++
 drivers/vdpa/vdpa_user/iova_domain.h |   94 +++
 drivers/vdpa/vdpa_user/vduse.h       |   66 ++
 drivers/vdpa/vdpa_user/vduse_dev.c   | 1028 ++++++++++++++++++++++++++
 include/uapi/linux/vduse.h           |   85 +++
 10 files changed, 1969 insertions(+)
 create mode 100644 drivers/vdpa/vdpa_user/Makefile
 create mode 100644 drivers/vdpa/vdpa_user/eventfd.c
 create mode 100644 drivers/vdpa/vdpa_user/eventfd.h
 create mode 100644 drivers/vdpa/vdpa_user/iova_domain.c
 create mode 100644 drivers/vdpa/vdpa_user/iova_domain.h
 create mode 100644 drivers/vdpa/vdpa_user/vduse.h
 create mode 100644 drivers/vdpa/vdpa_user/vduse_dev.c
 create mode 100644 include/uapi/linux/vduse.h

diff --git a/drivers/vdpa/Kconfig b/drivers/vdpa/Kconfig
index d7d32b656102..c1e51a434809 100644
--- a/drivers/vdpa/Kconfig
+++ b/drivers/vdpa/Kconfig
@@ -19,6 +19,14 @@ config VDPA_SIM
 	  to RX. This device is used for testing, prototyping and
 	  development of vDPA.
 
+config VDPA_USER
+	tristate "VDUSE (vDPA Device in Userspace) support"
+	depends on EVENTFD && MMU && HAS_DMA
+	default n
+	help
+	  With VDUSE it is possible to emulate a vDPA Device
+	  in a userspace program.
+
 config IFCVF
 	tristate "Intel IFC VF vDPA driver"
 	depends on PCI_MSI
diff --git a/drivers/vdpa/Makefile b/drivers/vdpa/Makefile
index d160e9b63a66..66e97778ad03 100644
--- a/drivers/vdpa/Makefile
+++ b/drivers/vdpa/Makefile
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_VDPA) += vdpa.o
 obj-$(CONFIG_VDPA_SIM) += vdpa_sim/
+obj-$(CONFIG_VDPA_USER) += vdpa_user/
 obj-$(CONFIG_IFCVF)    += ifcvf/
 obj-$(CONFIG_MLX5_VDPA) += mlx5/
diff --git a/drivers/vdpa/vdpa_user/Makefile b/drivers/vdpa/vdpa_user/Makefile
new file mode 100644
index 000000000000..b7645e36992b
--- /dev/null
+++ b/drivers/vdpa/vdpa_user/Makefile
@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0
+
+vduse-y := vduse_dev.o iova_domain.o eventfd.o
+
+obj-$(CONFIG_VDPA_USER) += vduse.o
diff --git a/drivers/vdpa/vdpa_user/eventfd.c b/drivers/vdpa/vdpa_user/eventfd.c
new file mode 100644
index 000000000000..dbffddb08908
--- /dev/null
+++ b/drivers/vdpa/vdpa_user/eventfd.c
@@ -0,0 +1,221 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Eventfd support for VDUSE
+ *
+ * Copyright (C) 2020 Bytedance Inc. and/or its affiliates. All rights reserved.
+ *
+ * Author: Xie Yongji <xieyongji@bytedance.com>
+ *
+ */
+
+#include <linux/eventfd.h>
+#include <linux/poll.h>
+#include <linux/wait.h>
+#include <linux/slab.h>
+#include <linux/file.h>
+#include <uapi/linux/vduse.h>
+
+#include "eventfd.h"
+
+static struct workqueue_struct *vduse_irqfd_cleanup_wq;
+
+static void vduse_virqfd_shutdown(struct work_struct *work)
+{
+	u64 cnt;
+	struct vduse_virqfd *virqfd = container_of(work,
+					struct vduse_virqfd, shutdown);
+
+	eventfd_ctx_remove_wait_queue(virqfd->ctx, &virqfd->wait, &cnt);
+	flush_work(&virqfd->inject);
+	eventfd_ctx_put(virqfd->ctx);
+	kfree(virqfd);
+}
+
+static void vduse_virqfd_inject(struct work_struct *work)
+{
+	struct vduse_virqfd *virqfd = container_of(work,
+					struct vduse_virqfd, inject);
+	struct vduse_virtqueue *vq = virqfd->vq;
+
+	spin_lock_irq(&vq->irq_lock);
+	if (vq->ready && vq->cb)
+		vq->cb(vq->private);
+	spin_unlock_irq(&vq->irq_lock);
+}
+
+static void virqfd_deactivate(struct vduse_virqfd *virqfd)
+{
+	queue_work(vduse_irqfd_cleanup_wq, &virqfd->shutdown);
+}
+
+static int vduse_virqfd_wakeup(wait_queue_entry_t *wait, unsigned int mode,
+				int sync, void *key)
+{
+	struct vduse_virqfd *virqfd = container_of(wait, struct vduse_virqfd, wait);
+	struct vduse_virtqueue *vq = virqfd->vq;
+
+	__poll_t flags = key_to_poll(key);
+
+	if (flags & EPOLLIN)
+		schedule_work(&virqfd->inject);
+
+	if (flags & EPOLLHUP) {
+		spin_lock(&vq->irq_lock);
+		if (vq->virqfd == virqfd) {
+			vq->virqfd = NULL;
+			virqfd_deactivate(virqfd);
+		}
+		spin_unlock(&vq->irq_lock);
+	}
+
+	return 0;
+}
+
+static void vduse_virqfd_ptable_queue_proc(struct file *file,
+			wait_queue_head_t *wqh, poll_table *pt)
+{
+	struct vduse_virqfd *virqfd = container_of(pt, struct vduse_virqfd, pt);
+
+	add_wait_queue(wqh, &virqfd->wait);
+}
+
+int vduse_virqfd_setup(struct vduse_dev *dev,
+			struct vduse_vq_eventfd *eventfd)
+{
+	struct vduse_virqfd *virqfd;
+	struct fd irqfd;
+	struct eventfd_ctx *ctx;
+	struct vduse_virtqueue *vq;
+	__poll_t events;
+	int ret;
+
+	if (eventfd->index >= dev->vq_num)
+		return -EINVAL;
+
+	vq = &dev->vqs[eventfd->index];
+	virqfd = kzalloc(sizeof(*virqfd), GFP_KERNEL);
+	if (!virqfd)
+		return -ENOMEM;
+
+	INIT_WORK(&virqfd->shutdown, vduse_virqfd_shutdown);
+	INIT_WORK(&virqfd->inject, vduse_virqfd_inject);
+
+	ret = -EBADF;
+	irqfd = fdget(eventfd->fd);
+	if (!irqfd.file)
+		goto err_fd;
+
+	ctx = eventfd_ctx_fileget(irqfd.file);
+	if (IS_ERR(ctx)) {
+		ret = PTR_ERR(ctx);
+		goto err_ctx;
+	}
+
+	virqfd->vq = vq;
+	virqfd->ctx = ctx;
+	spin_lock(&vq->irq_lock);
+	if (vq->virqfd)
+		virqfd_deactivate(virqfd);
+	vq->virqfd = virqfd;
+	spin_unlock(&vq->irq_lock);
+
+	init_waitqueue_func_entry(&virqfd->wait, vduse_virqfd_wakeup);
+	init_poll_funcptr(&virqfd->pt, vduse_virqfd_ptable_queue_proc);
+
+	events = vfs_poll(irqfd.file, &virqfd->pt);
+
+	/*
+	 * Check if there was an event already pending on the eventfd
+	 * before we registered and trigger it as if we didn't miss it.
+	 */
+	if (events & EPOLLIN)
+		schedule_work(&virqfd->inject);
+
+	fdput(irqfd);
+
+	return 0;
+err_ctx:
+	fdput(irqfd);
+err_fd:
+	kfree(virqfd);
+	return ret;
+}
+
+void vduse_virqfd_release(struct vduse_dev *dev)
+{
+	int i;
+
+	for (i = 0; i < dev->vq_num; i++) {
+		struct vduse_virtqueue *vq = &dev->vqs[i];
+
+		spin_lock(&vq->irq_lock);
+		if (vq->virqfd) {
+			virqfd_deactivate(vq->virqfd);
+			vq->virqfd = NULL;
+		}
+		spin_unlock(&vq->irq_lock);
+	}
+	flush_workqueue(vduse_irqfd_cleanup_wq);
+}
+
+int vduse_virqfd_init(void)
+{
+	vduse_irqfd_cleanup_wq = alloc_workqueue("vduse-irqfd-cleanup",
+						WQ_UNBOUND, 0);
+	if (!vduse_irqfd_cleanup_wq)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void vduse_virqfd_exit(void)
+{
+	destroy_workqueue(vduse_irqfd_cleanup_wq);
+}
+
+void vduse_vq_kick(struct vduse_virtqueue *vq)
+{
+	spin_lock(&vq->kick_lock);
+	if (vq->ready && vq->kickfd)
+		eventfd_signal(vq->kickfd, 1);
+	spin_unlock(&vq->kick_lock);
+}
+
+int vduse_kickfd_setup(struct vduse_dev *dev,
+			struct vduse_vq_eventfd *eventfd)
+{
+	struct eventfd_ctx *ctx;
+	struct vduse_virtqueue *vq;
+
+	if (eventfd->index >= dev->vq_num)
+		return -EINVAL;
+
+	vq = &dev->vqs[eventfd->index];
+	ctx = eventfd_ctx_fdget(eventfd->fd);
+	if (IS_ERR(ctx))
+		return PTR_ERR(ctx);
+
+	spin_lock(&vq->kick_lock);
+	if (vq->kickfd)
+		eventfd_ctx_put(vq->kickfd);
+	vq->kickfd = ctx;
+	spin_unlock(&vq->kick_lock);
+
+	return 0;
+}
+
+void vduse_kickfd_release(struct vduse_dev *dev)
+{
+	int i;
+
+	for (i = 0; i < dev->vq_num; i++) {
+		struct vduse_virtqueue *vq = &dev->vqs[i];
+
+		spin_lock(&vq->kick_lock);
+		if (vq->kickfd) {
+			eventfd_ctx_put(vq->kickfd);
+			vq->kickfd = NULL;
+		}
+		spin_unlock(&vq->kick_lock);
+	}
+}
diff --git a/drivers/vdpa/vdpa_user/eventfd.h b/drivers/vdpa/vdpa_user/eventfd.h
new file mode 100644
index 000000000000..14269ff27f47
--- /dev/null
+++ b/drivers/vdpa/vdpa_user/eventfd.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Eventfd support for VDUSE
+ *
+ * Copyright (C) 2020 Bytedance Inc. and/or its affiliates. All rights reserved.
+ *
+ * Author: Xie Yongji <xieyongji@bytedance.com>
+ *
+ */
+
+#ifndef _VDUSE_EVENTFD_H
+#define _VDUSE_EVENTFD_H
+
+#include <linux/eventfd.h>
+#include <linux/poll.h>
+#include <linux/wait.h>
+#include <uapi/linux/vduse.h>
+
+#include "vduse.h"
+
+struct vduse_dev;
+
+struct vduse_virqfd {
+	struct eventfd_ctx *ctx;
+	struct vduse_virtqueue *vq;
+	struct work_struct inject;
+	struct work_struct shutdown;
+	wait_queue_entry_t wait;
+	poll_table pt;
+};
+
+int vduse_virqfd_setup(struct vduse_dev *dev,
+			struct vduse_vq_eventfd *eventfd);
+
+void vduse_virqfd_release(struct vduse_dev *dev);
+
+int vduse_virqfd_init(void);
+
+void vduse_virqfd_exit(void);
+
+void vduse_vq_kick(struct vduse_virtqueue *vq);
+
+int vduse_kickfd_setup(struct vduse_dev *dev,
+			struct vduse_vq_eventfd *eventfd);
+
+void vduse_kickfd_release(struct vduse_dev *dev);
+
+#endif /* _VDUSE_EVENTFD_H */
diff --git a/drivers/vdpa/vdpa_user/iova_domain.c b/drivers/vdpa/vdpa_user/iova_domain.c
new file mode 100644
index 000000000000..a274f78f00d2
--- /dev/null
+++ b/drivers/vdpa/vdpa_user/iova_domain.c
@@ -0,0 +1,413 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MMU-based IOMMU implementation
+ *
+ * Copyright (C) 2020 Bytedance Inc. and/or its affiliates. All rights reserved.
+ *
+ * Author: Xie Yongji <xieyongji@bytedance.com>
+ *
+ */
+
+#include <linux/wait.h>
+#include <linux/slab.h>
+#include <linux/interval_tree.h>
+#include <linux/genalloc.h>
+#include <linux/dma-mapping.h>
+
+#include "iova_domain.h"
+
+#define IOVA_CHUNK_SHIFT 26
+#define IOVA_CHUNK_SIZE (_AC(1, UL) << IOVA_CHUNK_SHIFT)
+#define IOVA_CHUNK_MASK (~(IOVA_CHUNK_SIZE - 1))
+
+#define IOVA_MIN_SIZE (IOVA_CHUNK_SIZE >> 1)
+
+#define IOVA_ALLOC_ORDER 9
+#define IOVA_ALLOC_SIZE (1 << IOVA_ALLOC_ORDER)
+
+struct vduse_mmap_vma {
+	struct vm_area_struct *vma;
+	struct list_head list;
+};
+
+static inline struct page *
+vduse_domain_get_bounce_page(struct vduse_iova_domain *domain,
+				unsigned long iova)
+{
+	unsigned long index = iova >> IOVA_CHUNK_SHIFT;
+	unsigned long chunkoff = iova & ~IOVA_CHUNK_MASK;
+	unsigned long pgindex = chunkoff >> PAGE_SHIFT;
+
+	return domain->chunks[index].bounce_pages[pgindex];
+}
+
+static inline void
+vduse_domain_set_bounce_page(struct vduse_iova_domain *domain,
+				unsigned long iova, struct page *page)
+{
+	unsigned long index = iova >> IOVA_CHUNK_SHIFT;
+	unsigned long chunkoff = iova & ~IOVA_CHUNK_MASK;
+	unsigned long pgindex = chunkoff >> PAGE_SHIFT;
+
+	domain->chunks[index].bounce_pages[pgindex] = page;
+}
+
+static int
+vduse_domain_free_bounce_pages(struct vduse_iova_domain *domain,
+				unsigned long iova, size_t size)
+{
+	struct page *page;
+	size_t walk_sz = 0;
+	int frees = 0;
+
+	while (walk_sz < size) {
+		page = vduse_domain_get_bounce_page(domain, iova);
+		if (page) {
+			vduse_domain_set_bounce_page(domain, iova, NULL);
+			put_page(page);
+			frees++;
+		}
+		iova += PAGE_SIZE;
+		walk_sz += PAGE_SIZE;
+	}
+
+	return frees;
+}
+
+int vduse_domain_add_vma(struct vduse_iova_domain *domain,
+				struct vm_area_struct *vma)
+{
+	unsigned long size = vma->vm_end - vma->vm_start;
+	struct vduse_mmap_vma *mmap_vma;
+
+	if (WARN_ON(size != domain->size))
+		return -EINVAL;
+
+	mmap_vma = kmalloc(sizeof(*mmap_vma), GFP_KERNEL);
+	if (!mmap_vma)
+		return -ENOMEM;
+
+	mmap_vma->vma = vma;
+	mutex_lock(&domain->vma_lock);
+	list_add(&mmap_vma->list, &domain->vma_list);
+	mutex_unlock(&domain->vma_lock);
+
+	return 0;
+}
+
+void vduse_domain_remove_vma(struct vduse_iova_domain *domain,
+				struct vm_area_struct *vma)
+{
+	struct vduse_mmap_vma *mmap_vma;
+
+	mutex_lock(&domain->vma_lock);
+	list_for_each_entry(mmap_vma, &domain->vma_list, list) {
+		if (mmap_vma->vma == vma) {
+			list_del(&mmap_vma->list);
+			kfree(mmap_vma);
+			break;
+		}
+	}
+	mutex_unlock(&domain->vma_lock);
+}
+
+int vduse_domain_add_mapping(struct vduse_iova_domain *domain,
+				unsigned long iova, unsigned long orig,
+				size_t size, enum dma_data_direction dir)
+{
+	struct vduse_iova_map *map;
+
+	map = kzalloc(sizeof(struct vduse_iova_map), GFP_ATOMIC);
+	if (!map)
+		return -ENOMEM;
+
+	map->iova.start = iova;
+	map->iova.last = iova + size - 1;
+	map->orig = orig;
+	map->size = size;
+	map->dir = dir;
+
+	spin_lock(&domain->map_lock);
+	interval_tree_insert(&map->iova, &domain->mappings);
+	spin_unlock(&domain->map_lock);
+
+	return 0;
+}
+
+struct vduse_iova_map *
+vduse_domain_get_mapping(struct vduse_iova_domain *domain,
+			unsigned long iova, size_t size)
+{
+	struct interval_tree_node *node;
+	struct vduse_iova_map *map = NULL;
+	unsigned long last = iova + size - 1;
+
+	spin_lock(&domain->map_lock);
+	node = interval_tree_iter_first(&domain->mappings, iova, last);
+	if (node)
+		map = container_of(node, struct vduse_iova_map, iova);
+	spin_unlock(&domain->map_lock);
+
+	return map;
+}
+
+void vduse_domain_remove_mapping(struct vduse_iova_domain *domain,
+				struct vduse_iova_map *map)
+{
+	spin_lock(&domain->map_lock);
+	interval_tree_remove(&map->iova, &domain->mappings);
+	spin_unlock(&domain->map_lock);
+}
+
+void vduse_domain_unmap(struct vduse_iova_domain *domain,
+			unsigned long iova, size_t size)
+{
+	struct vduse_mmap_vma *mmap_vma;
+	unsigned long uaddr;
+
+	mutex_lock(&domain->vma_lock);
+	list_for_each_entry(mmap_vma, &domain->vma_list, list) {
+		mmap_read_lock(mmap_vma->vma->vm_mm);
+		uaddr = iova + mmap_vma->vma->vm_start;
+		zap_page_range(mmap_vma->vma, uaddr, size);
+		mmap_read_unlock(mmap_vma->vma->vm_mm);
+	}
+	mutex_unlock(&domain->vma_lock);
+}
+
+int vduse_domain_direct_map(struct vduse_iova_domain *domain,
+			struct vm_area_struct *vma, unsigned long iova)
+{
+	unsigned long uaddr = iova + vma->vm_start;
+	unsigned long start = iova & PAGE_MASK;
+	unsigned long last = start + PAGE_SIZE - 1;
+	unsigned long offset;
+	struct vduse_iova_map *map;
+	struct interval_tree_node *node;
+	struct page *page = NULL;
+
+	spin_lock(&domain->map_lock);
+	node = interval_tree_iter_first(&domain->mappings, start, last);
+	if (node) {
+		map = container_of(node, struct vduse_iova_map, iova);
+		offset = last - map->iova.start;
+		page = virt_to_page(map->orig + offset);
+	}
+	spin_unlock(&domain->map_lock);
+
+	return page ? vm_insert_page(vma, uaddr, page) : -EFAULT;
+}
+
+void vduse_domain_bounce(struct vduse_iova_domain *domain,
+			unsigned long iova, unsigned long orig,
+			size_t size, enum dma_data_direction dir)
+{
+	unsigned int offset = offset_in_page(iova);
+
+	while (size) {
+		struct page *p = vduse_domain_get_bounce_page(domain, iova);
+		size_t copy_len = min_t(size_t, PAGE_SIZE - offset, size);
+		void *addr;
+
+		if (p) {
+			addr = page_address(p) + offset;
+			if (dir == DMA_TO_DEVICE)
+				memcpy(addr, (void *)orig, copy_len);
+			else if (dir == DMA_FROM_DEVICE)
+				memcpy((void *)orig, addr, copy_len);
+		}
+		size -= copy_len;
+		orig += copy_len;
+		iova += copy_len;
+		offset = 0;
+	}
+}
+
+int vduse_domain_bounce_map(struct vduse_iova_domain *domain,
+			struct vm_area_struct *vma, unsigned long iova)
+{
+	unsigned long uaddr = iova + vma->vm_start;
+	unsigned long start = iova & PAGE_MASK;
+	unsigned long last = start + PAGE_SIZE - 1;
+	struct vduse_iova_map *map;
+	struct interval_tree_node *node;
+	struct page *page;
+
+	page = alloc_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	spin_lock(&domain->map_lock);
+	if (vduse_domain_get_bounce_page(domain, iova))
+		goto unlock;
+
+	node = interval_tree_iter_first(&domain->mappings, start, last);
+	if (!node)
+		goto unlock;
+
+	while (node) {
+		unsigned int src_offset = 0, dst_offset = 0;
+		void *src, *dst;
+		size_t copy_len;
+
+		map = container_of(node, struct vduse_iova_map, iova);
+		node = interval_tree_iter_next(node, start, last);
+		if (map->dir == DMA_FROM_DEVICE)
+			continue;
+
+		if (start > map->iova.start)
+			src_offset = start - map->iova.start;
+		else
+			dst_offset = map->iova.start - start;
+		src = (void *)(map->orig + src_offset);
+		dst = page_address(page) + dst_offset;
+		copy_len = min_t(size_t, map->size - src_offset,
+				PAGE_SIZE - dst_offset);
+		memcpy(dst, src, copy_len);
+	}
+	get_page(page);
+	vduse_domain_set_bounce_page(domain, iova, page);
+unlock:
+	put_page(page);
+	page = vduse_domain_get_bounce_page(domain, iova);
+	spin_unlock(&domain->map_lock);
+
+	return page ? vm_insert_page(vma, uaddr, page) : -EFAULT;
+}
+
+bool vduse_domain_is_direct_map(struct vduse_iova_domain *domain,
+				unsigned long iova)
+{
+	unsigned long index = iova >> IOVA_CHUNK_SHIFT;
+	struct vduse_iova_chunk *chunk = &domain->chunks[index];
+
+	return atomic_read(&chunk->map_type) == TYPE_DIRECT_MAP;
+}
+
+unsigned long vduse_domain_alloc_iova(struct vduse_iova_domain *domain,
+					size_t size, enum iova_map_type type)
+{
+	struct vduse_iova_chunk *chunk;
+	unsigned long iova = 0;
+	int align = (type == TYPE_DIRECT_MAP) ? PAGE_SIZE : IOVA_ALLOC_SIZE;
+	struct genpool_data_align data = { .align = align };
+	int i;
+
+	for (i = 0; i < domain->chunk_num; i++) {
+		chunk = &domain->chunks[i];
+		if (unlikely(atomic_read(&chunk->map_type) == TYPE_NONE))
+			atomic_cmpxchg(&chunk->map_type, TYPE_NONE, type);
+
+		if (atomic_read(&chunk->map_type) != type)
+			continue;
+
+		iova = gen_pool_alloc_algo(chunk->pool, size,
+					gen_pool_first_fit_align, &data);
+		if (iova)
+			break;
+	}
+
+	return iova;
+}
+
+void vduse_domain_free_iova(struct vduse_iova_domain *domain,
+				unsigned long iova, size_t size)
+{
+	unsigned long index = iova >> IOVA_CHUNK_SHIFT;
+	struct vduse_iova_chunk *chunk = &domain->chunks[index];
+
+	gen_pool_free(chunk->pool, iova, size);
+}
+
+static void vduse_iova_chunk_cleanup(struct vduse_iova_chunk *chunk)
+{
+	vfree(chunk->bounce_pages);
+	gen_pool_destroy(chunk->pool);
+}
+
+void vduse_iova_domain_destroy(struct vduse_iova_domain *domain)
+{
+	struct vduse_iova_chunk *chunk;
+	int i;
+
+	for (i = 0; i < domain->chunk_num; i++) {
+		chunk = &domain->chunks[i];
+		vduse_domain_free_bounce_pages(domain,
+					chunk->start, IOVA_CHUNK_SIZE);
+		vduse_iova_chunk_cleanup(chunk);
+	}
+
+	mutex_destroy(&domain->vma_lock);
+	kfree(domain->chunks);
+	kfree(domain);
+}
+
+static int vduse_iova_chunk_init(struct vduse_iova_chunk *chunk,
+				unsigned long addr, size_t size)
+{
+	int ret;
+	int pages = size >> PAGE_SHIFT;
+
+	chunk->pool = gen_pool_create(IOVA_ALLOC_ORDER, -1);
+	if (!chunk->pool)
+		return -ENOMEM;
+
+	/* addr 0 is used in allocation failure case */
+	if (addr == 0)
+		addr += IOVA_ALLOC_SIZE;
+
+	ret = gen_pool_add(chunk->pool, addr, size, -1);
+	if (ret)
+		goto err;
+
+	ret = -ENOMEM;
+	chunk->bounce_pages = vzalloc(pages * sizeof(struct page *));
+	if (!chunk->bounce_pages)
+		goto err;
+
+	chunk->start = addr;
+	atomic_set(&chunk->map_type, TYPE_NONE);
+
+	return 0;
+err:
+	gen_pool_destroy(chunk->pool);
+	return ret;
+}
+
+struct vduse_iova_domain *vduse_iova_domain_create(size_t size)
+{
+	int j, i = 0;
+	struct vduse_iova_domain *domain;
+	unsigned long num = size >> IOVA_CHUNK_SHIFT;
+	unsigned long addr = 0;
+
+	if (size < IOVA_MIN_SIZE || size & ~IOVA_CHUNK_MASK)
+		return NULL;
+
+	domain = kzalloc(sizeof(*domain), GFP_KERNEL);
+	if (!domain)
+		return NULL;
+
+	domain->chunks = kcalloc(num, sizeof(struct vduse_iova_chunk), GFP_KERNEL);
+	if (!domain->chunks)
+		goto err;
+
+	for (i = 0; i < num; i++, addr += IOVA_CHUNK_SIZE)
+		if (vduse_iova_chunk_init(&domain->chunks[i], addr,
+					IOVA_CHUNK_SIZE))
+			goto err;
+
+	domain->chunk_num = num;
+	domain->size = size;
+	domain->mappings = RB_ROOT_CACHED;
+	INIT_LIST_HEAD(&domain->vma_list);
+	mutex_init(&domain->vma_lock);
+
+	return domain;
+err:
+	for (j = 0; j < i; j++)
+		vduse_iova_chunk_cleanup(&domain->chunks[j]);
+	kfree(domain);
+
+	return NULL;
+}
diff --git a/drivers/vdpa/vdpa_user/iova_domain.h b/drivers/vdpa/vdpa_user/iova_domain.h
new file mode 100644
index 000000000000..7ae60c0e50ec
--- /dev/null
+++ b/drivers/vdpa/vdpa_user/iova_domain.h
@@ -0,0 +1,94 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * MMU-based IOMMU implementation
+ *
+ * Copyright (C) 2020 Bytedance Inc. and/or its affiliates. All rights reserved.
+ *
+ * Author: Xie Yongji <xieyongji@bytedance.com>
+ *
+ */
+
+#ifndef _VDUSE_IOVA_DOMAIN_H
+#define _VDUSE_IOVA_DOMAIN_H
+
+#include <linux/interval_tree.h>
+#include <linux/genalloc.h>
+#include <linux/dma-mapping.h>
+
+enum iova_map_type {
+	TYPE_NONE,
+	TYPE_DIRECT_MAP,
+	TYPE_BOUNCE_MAP,
+};
+
+struct vduse_iova_chunk {
+	struct gen_pool *pool;
+	struct page **bounce_pages;
+	unsigned long start;
+	atomic_t map_type;
+};
+
+struct vduse_iova_domain {
+	struct vduse_iova_chunk *chunks;
+	int chunk_num;
+	size_t size;
+	struct rb_root_cached mappings;
+	spinlock_t map_lock;
+	struct mutex vma_lock;
+	struct list_head vma_list;
+};
+
+struct vduse_iova_map {
+	struct interval_tree_node iova;
+	unsigned long orig;
+	size_t size;
+	enum dma_data_direction dir;
+};
+
+int vduse_domain_add_vma(struct vduse_iova_domain *domain,
+				struct vm_area_struct *vma);
+
+void vduse_domain_remove_vma(struct vduse_iova_domain *domain,
+				struct vm_area_struct *vma);
+
+int vduse_domain_add_mapping(struct vduse_iova_domain *domain,
+				unsigned long iova, unsigned long orig,
+				size_t size, enum dma_data_direction dir);
+
+struct vduse_iova_map *
+vduse_domain_get_mapping(struct vduse_iova_domain *domain,
+			unsigned long iova, size_t size);
+
+void vduse_domain_remove_mapping(struct vduse_iova_domain *domain,
+				struct vduse_iova_map *map);
+
+void vduse_domain_unmap(struct vduse_iova_domain *domain,
+			unsigned long iova, size_t size);
+
+int vduse_domain_direct_map(struct vduse_iova_domain *domain,
+			struct vm_area_struct *vma, unsigned long iova);
+
+void vduse_domain_bounce(struct vduse_iova_domain *domain,
+			unsigned long iova, unsigned long orig,
+			size_t size, enum dma_data_direction dir);
+
+int vduse_domain_bounce_map(struct vduse_iova_domain *domain,
+			struct vm_area_struct *vma, unsigned long iova);
+
+bool vduse_domain_is_direct_map(struct vduse_iova_domain *domain,
+				unsigned long iova);
+
+unsigned long vduse_domain_alloc_iova(struct vduse_iova_domain *domain,
+					size_t size, enum iova_map_type type);
+
+void vduse_domain_free_iova(struct vduse_iova_domain *domain,
+				unsigned long iova, size_t size);
+
+bool vduse_domain_is_direct_map(struct vduse_iova_domain *domain,
+				unsigned long iova);
+
+void vduse_iova_domain_destroy(struct vduse_iova_domain *domain);
+
+struct vduse_iova_domain *vduse_iova_domain_create(size_t size);
+
+#endif /* _VDUSE_IOVA_DOMAIN_H */
diff --git a/drivers/vdpa/vdpa_user/vduse.h b/drivers/vdpa/vdpa_user/vduse.h
new file mode 100644
index 000000000000..3bd52f668ab3
--- /dev/null
+++ b/drivers/vdpa/vdpa_user/vduse.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * VDUSE: vDPA Device in Userspace
+ *
+ * Copyright (C) 2020 Bytedance Inc. and/or its affiliates. All rights reserved.
+ *
+ * Author: Xie Yongji <xieyongji@bytedance.com>
+ *
+ */
+
+#ifndef _VDUSE_H
+#define _VDUSE_H
+
+#include <linux/eventfd.h>
+#include <linux/wait.h>
+#include <linux/vdpa.h>
+
+#include "iova_domain.h"
+#include "eventfd.h"
+
+struct vduse_virtqueue {
+	u16 index;
+	u32 num;
+	u64 desc_addr;
+	u64 device_addr;
+	u64 driver_addr;
+	bool ready;
+	spinlock_t kick_lock;
+	spinlock_t irq_lock;
+	struct eventfd_ctx *kickfd;
+	struct vduse_virqfd *virqfd;
+	void *private;
+	irqreturn_t (*cb)(void *data);
+};
+
+struct vduse_dev;
+
+struct vduse_vdpa {
+	struct vdpa_device vdpa;
+	struct vduse_dev *dev;
+	struct work_struct start_work;
+	struct work_struct stop_work;
+	bool stopping;
+};
+
+struct vduse_dev {
+	struct vduse_vdpa *vdev;
+	struct vduse_virtqueue *vqs;
+	struct vduse_iova_domain *domain;
+	struct mutex lock;
+	spinlock_t msg_lock;
+	atomic64_t msg_unique;
+	wait_queue_head_t waitq;
+	struct list_head send_list;
+	struct list_head recv_list;
+	struct list_head list;
+	bool connected;
+	u32 id;
+	u16 vq_size_max;
+	u16 vq_num;
+	u32 vq_align;
+	u32 device_id;
+	u32 vendor_id;
+};
+
+#endif /* _VDUSE_H_ */
diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
new file mode 100644
index 000000000000..6787ba66725c
--- /dev/null
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -0,0 +1,1028 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * VDUSE: vDPA Device in Userspace
+ *
+ * Copyright (C) 2020 Bytedance Inc. and/or its affiliates. All rights reserved.
+ *
+ * Author: Xie Yongji <xieyongji@bytedance.com>
+ *
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/miscdevice.h>
+#include <linux/device.h>
+#include <linux/eventfd.h>
+#include <linux/slab.h>
+#include <linux/wait.h>
+#include <linux/dma-mapping.h>
+#include <linux/anon_inodes.h>
+#include <linux/file.h>
+#include <linux/uio.h>
+#include <linux/vdpa.h>
+#include <uapi/linux/vduse.h>
+#include <uapi/linux/virtio_config.h>
+
+#include "vduse.h"
+
+#define DRV_VERSION  "1.0"
+#define DRV_AUTHOR   "Yongji Xie <xieyongji@bytedance.com>"
+#define DRV_DESC     "vDPA Device in Userspace"
+#define DRV_LICENSE  "GPL v2"
+
+struct vduse_dev_msg {
+	struct vduse_dev_request req;
+	struct vduse_dev_response resp;
+	struct list_head list;
+	wait_queue_head_t waitq;
+	bool completed;
+	refcount_t refcnt;
+};
+
+static struct workqueue_struct *vduse_vdpa_wq;
+static DEFINE_MUTEX(vduse_lock);
+static LIST_HEAD(vduse_devs);
+
+static inline struct vduse_dev *vdpa_to_vduse(struct vdpa_device *vdpa)
+{
+	struct vduse_vdpa *vdev = container_of(vdpa, struct vduse_vdpa, vdpa);
+
+	return vdev->dev;
+}
+
+static inline struct vduse_dev *dev_to_vduse(struct device *dev)
+{
+	struct vdpa_device *vdpa = dev_to_vdpa(dev);
+
+	return vdpa_to_vduse(vdpa);
+}
+
+static struct vduse_dev_msg *vduse_dev_new_msg(struct vduse_dev *dev, int type)
+{
+	struct vduse_dev_msg *msg = kzalloc(sizeof(*msg),
+					GFP_KERNEL | __GFP_NOFAIL);
+
+	msg->req.type = type;
+	msg->req.unique = atomic64_fetch_inc(&dev->msg_unique);
+	init_waitqueue_head(&msg->waitq);
+	refcount_set(&msg->refcnt, 1);
+
+	return msg;
+}
+
+static void vduse_dev_msg_get(struct vduse_dev_msg *msg)
+{
+	refcount_inc(&msg->refcnt);
+}
+
+static void vduse_dev_msg_put(struct vduse_dev_msg *msg)
+{
+	if (refcount_dec_and_test(&msg->refcnt))
+		kfree(msg);
+}
+
+static struct vduse_dev_msg *vduse_dev_find_msg(struct vduse_dev *dev,
+						struct list_head *head,
+						uint32_t unique)
+{
+	struct vduse_dev_msg *tmp, *msg = NULL;
+
+	spin_lock(&dev->msg_lock);
+	list_for_each_entry(tmp, head, list) {
+		if (tmp->req.unique == unique) {
+			msg = tmp;
+			list_del(&tmp->list);
+			break;
+		}
+	}
+	spin_unlock(&dev->msg_lock);
+
+	return msg;
+}
+
+static struct vduse_dev_msg *vduse_dev_dequeue_msg(struct vduse_dev *dev,
+						struct list_head *head)
+{
+	struct vduse_dev_msg *msg = NULL;
+
+	spin_lock(&dev->msg_lock);
+	if (!list_empty(head)) {
+		msg = list_first_entry(head, struct vduse_dev_msg, list);
+		list_del(&msg->list);
+	}
+	spin_unlock(&dev->msg_lock);
+
+	return msg;
+}
+
+static void vduse_dev_enqueue_msg(struct vduse_dev *dev,
+			struct vduse_dev_msg *msg, struct list_head *head)
+{
+	spin_lock(&dev->msg_lock);
+	list_add_tail(&msg->list, head);
+	spin_unlock(&dev->msg_lock);
+}
+
+static int vduse_dev_msg_sync(struct vduse_dev *dev, struct vduse_dev_msg *msg)
+{
+	int ret;
+
+	vduse_dev_enqueue_msg(dev, msg, &dev->send_list);
+	wake_up(&dev->waitq);
+	wait_event(msg->waitq, msg->completed);
+	/* coupled with smp_wmb() in vduse_dev_msg_complete() */
+	smp_rmb();
+	ret = msg->resp.result;
+
+	return ret;
+}
+
+static void vduse_dev_msg_complete(struct vduse_dev_msg *msg,
+					struct vduse_dev_response *resp)
+{
+	vduse_dev_msg_get(msg);
+	memcpy(&msg->resp, resp, sizeof(*resp));
+	/* coupled with smp_rmb() in vduse_dev_msg_sync() */
+	smp_wmb();
+	msg->completed = 1;
+	wake_up(&msg->waitq);
+	vduse_dev_msg_put(msg);
+}
+
+static u64 vduse_dev_get_features(struct vduse_dev *dev)
+{
+	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_GET_FEATURES);
+	u64 features;
+
+	vduse_dev_msg_sync(dev, msg);
+	features = msg->resp.features;
+	vduse_dev_msg_put(msg);
+
+	return features;
+}
+
+static int vduse_dev_set_features(struct vduse_dev *dev, u64 features)
+{
+	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_SET_FEATURES);
+	int ret;
+
+	msg->req.size = sizeof(features);
+	msg->req.features = features;
+
+	ret = vduse_dev_msg_sync(dev, msg);
+	vduse_dev_msg_put(msg);
+
+	return ret;
+}
+
+static u8 vduse_dev_get_status(struct vduse_dev *dev)
+{
+	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_GET_STATUS);
+	u8 status;
+
+	vduse_dev_msg_sync(dev, msg);
+	status = msg->resp.status;
+	vduse_dev_msg_put(msg);
+
+	return status;
+}
+
+static void vduse_dev_set_status(struct vduse_dev *dev, u8 status)
+{
+	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_SET_STATUS);
+
+	msg->req.size = sizeof(status);
+	msg->req.status = status;
+
+	vduse_dev_msg_sync(dev, msg);
+	vduse_dev_msg_put(msg);
+}
+
+static void vduse_dev_get_config(struct vduse_dev *dev, unsigned int offset,
+					void *buf, unsigned int len)
+{
+	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_GET_CONFIG);
+
+	WARN_ON(len > sizeof(msg->req.config.data));
+
+	msg->req.size = sizeof(struct vduse_dev_config_data);
+	msg->req.config.offset = offset;
+	msg->req.config.len = len;
+	vduse_dev_msg_sync(dev, msg);
+	memcpy(buf, msg->resp.config.data, len);
+	vduse_dev_msg_put(msg);
+}
+
+static void vduse_dev_set_config(struct vduse_dev *dev, unsigned int offset,
+					const void *buf, unsigned int len)
+{
+	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_SET_CONFIG);
+
+	WARN_ON(len > sizeof(msg->req.config.data));
+
+	msg->req.size = sizeof(struct vduse_dev_config_data);
+	msg->req.config.offset = offset;
+	msg->req.config.len = len;
+	memcpy(msg->req.config.data, buf, len);
+	vduse_dev_msg_sync(dev, msg);
+	vduse_dev_msg_put(msg);
+}
+
+static void vduse_dev_set_vq_state(struct vduse_dev *dev,
+				   struct vduse_virtqueue *vq)
+{
+	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_SET_VQ_STATE);
+
+	msg->req.size = sizeof(struct vduse_vq_state);
+	msg->req.vq_state.index = vq->index;
+	msg->req.vq_state.num = vq->num;
+	msg->req.vq_state.desc_addr = vq->desc_addr;
+	msg->req.vq_state.driver_addr = vq->driver_addr;
+	msg->req.vq_state.device_addr = vq->device_addr;
+	msg->req.vq_state.ready = vq->ready;
+
+	vduse_dev_msg_sync(dev, msg);
+	vduse_dev_msg_put(msg);
+}
+
+static ssize_t vduse_dev_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct file *file = iocb->ki_filp;
+	struct vduse_dev *dev = file->private_data;
+	struct vduse_dev_msg *msg;
+	int size = sizeof(struct vduse_dev_request);
+	ssize_t ret = 0;
+
+	if (iov_iter_count(to) < size)
+		return 0;
+
+	while (1) {
+		if (!dev->vdev)
+			return -EPERM;
+
+		msg = vduse_dev_dequeue_msg(dev, &dev->send_list);
+		if (msg)
+			break;
+
+		if (file->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+
+		ret = wait_event_interruptible_exclusive(dev->waitq,
+			!dev->vdev || !list_empty(&dev->send_list));
+		if (ret)
+			return ret;
+	}
+	ret = copy_to_iter(&msg->req, size, to);
+	if (ret != size) {
+		vduse_dev_enqueue_msg(dev, msg, &dev->send_list);
+		return -EFAULT;
+	}
+	vduse_dev_enqueue_msg(dev, msg, &dev->recv_list);
+
+	return ret;
+}
+
+static ssize_t vduse_dev_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct vduse_dev *dev = file->private_data;
+	struct vduse_dev_response resp;
+	struct vduse_dev_msg *msg;
+	size_t ret;
+
+	if (!dev->vdev)
+		return -EPERM;
+
+	ret = copy_from_iter(&resp, sizeof(resp), from);
+	if (ret != sizeof(resp))
+		return -EINVAL;
+
+	msg = vduse_dev_find_msg(dev, &dev->recv_list, resp.unique);
+	if (!msg)
+		return -EINVAL;
+
+	vduse_dev_msg_complete(msg, &resp);
+
+	return ret;
+}
+
+static __poll_t vduse_dev_poll(struct file *file, poll_table *wait)
+{
+	struct vduse_dev *dev = file->private_data;
+	__poll_t mask = 0;
+
+	poll_wait(file, &dev->waitq, wait);
+
+	if (!dev->vdev)
+		mask = EPOLLERR;
+	else if (!list_empty(&dev->send_list))
+		mask |= EPOLLIN | EPOLLRDNORM;
+
+	return mask;
+}
+
+static void vduse_dev_reset(struct vduse_dev *dev)
+{
+	int i;
+
+	for (i = 0; i < dev->vq_num; i++) {
+		struct vduse_virtqueue *vq = &dev->vqs[i];
+
+		spin_lock(&vq->irq_lock);
+		vq->ready = false;
+		vq->desc_addr = 0;
+		vq->driver_addr = 0;
+		vq->device_addr = 0;
+		vq->cb = NULL;
+		vq->private = NULL;
+		spin_unlock(&vq->irq_lock);
+	}
+}
+
+static int vduse_vdpa_set_vq_address(struct vdpa_device *vdpa, u16 idx,
+				u64 desc_area, u64 driver_area,
+				u64 device_area)
+{
+	struct vduse_dev *vduse_dev = vdpa_to_vduse(vdpa);
+	struct vduse_virtqueue *vq = &vduse_dev->vqs[idx];
+
+	vq->desc_addr = desc_area;
+	vq->driver_addr = driver_area;
+	vq->device_addr = device_area;
+
+	return 0;
+}
+
+static void vduse_vdpa_kick_vq(struct vdpa_device *vdpa, u16 idx)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+	struct vduse_virtqueue *vq = &dev->vqs[idx];
+
+	vduse_vq_kick(vq);
+}
+
+static void vduse_vdpa_set_vq_cb(struct vdpa_device *vdpa, u16 idx,
+			      struct vdpa_callback *cb)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+	struct vduse_virtqueue *vq = &dev->vqs[idx];
+
+	vq->cb = cb->callback;
+	vq->private = cb->private;
+}
+
+static void vduse_vdpa_set_vq_num(struct vdpa_device *vdpa, u16 idx, u32 num)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+	struct vduse_virtqueue *vq = &dev->vqs[idx];
+
+	vq->num = num;
+}
+
+static void vduse_vdpa_set_vq_ready(struct vdpa_device *vdpa,
+					u16 idx, bool ready)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+	struct vduse_virtqueue *vq = &dev->vqs[idx];
+
+	vq->ready = ready;
+	vduse_dev_set_vq_state(dev, vq);
+}
+
+static bool vduse_vdpa_get_vq_ready(struct vdpa_device *vdpa, u16 idx)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+	struct vduse_virtqueue *vq = &dev->vqs[idx];
+
+	return vq->ready;
+}
+
+static u32 vduse_vdpa_get_vq_align(struct vdpa_device *vdpa)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+
+	return dev->vq_align;
+}
+
+static u64 vduse_vdpa_get_features(struct vdpa_device *vdpa)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+	u64 fixed = (1ULL << VIRTIO_F_ACCESS_PLATFORM);
+
+	return (vduse_dev_get_features(dev) | fixed);
+}
+
+static int vduse_vdpa_set_features(struct vdpa_device *vdpa, u64 features)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+
+	return vduse_dev_set_features(dev, features);
+}
+
+static void vduse_vdpa_set_config_cb(struct vdpa_device *vdpa,
+				  struct vdpa_callback *cb)
+{
+	/* We don't support config interrupt */
+}
+
+static u16 vduse_vdpa_get_vq_num_max(struct vdpa_device *vdpa)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+
+	return dev->vq_size_max;
+}
+
+static u32 vduse_vdpa_get_device_id(struct vdpa_device *vdpa)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+
+	return dev->device_id;
+}
+
+static u32 vduse_vdpa_get_vendor_id(struct vdpa_device *vdpa)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+
+	return dev->vendor_id;
+}
+
+static u8 vduse_vdpa_get_status(struct vdpa_device *vdpa)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+
+	return vduse_dev_get_status(dev);
+}
+
+static void vduse_vdpa_set_status(struct vdpa_device *vdpa, u8 status)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+
+	if (status == 0)
+		vduse_dev_reset(dev);
+
+	vduse_dev_set_status(dev, status);
+}
+
+static void vduse_vdpa_get_config(struct vdpa_device *vdpa, unsigned int offset,
+			     void *buf, unsigned int len)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+
+	vduse_dev_get_config(dev, offset, buf, len);
+}
+
+static void vduse_vdpa_set_config(struct vdpa_device *vdpa, unsigned int offset,
+			const void *buf, unsigned int len)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+
+	vduse_dev_set_config(dev, offset, buf, len);
+}
+
+static void vduse_vdpa_free(struct vdpa_device *vdpa)
+{
+	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
+
+	vduse_kickfd_release(dev);
+	vduse_virqfd_release(dev);
+
+	WARN_ON(!list_empty(&dev->send_list));
+	WARN_ON(!list_empty(&dev->recv_list));
+	dev->vdev = NULL;
+	wake_up_all(&dev->waitq);
+}
+
+static const struct vdpa_config_ops vduse_vdpa_config_ops = {
+	.set_vq_address		= vduse_vdpa_set_vq_address,
+	.kick_vq		= vduse_vdpa_kick_vq,
+	.set_vq_cb		= vduse_vdpa_set_vq_cb,
+	.set_vq_num             = vduse_vdpa_set_vq_num,
+	.set_vq_ready		= vduse_vdpa_set_vq_ready,
+	.get_vq_ready		= vduse_vdpa_get_vq_ready,
+	.get_vq_align		= vduse_vdpa_get_vq_align,
+	.get_features		= vduse_vdpa_get_features,
+	.set_features		= vduse_vdpa_set_features,
+	.set_config_cb		= vduse_vdpa_set_config_cb,
+	.get_vq_num_max		= vduse_vdpa_get_vq_num_max,
+	.get_device_id		= vduse_vdpa_get_device_id,
+	.get_vendor_id		= vduse_vdpa_get_vendor_id,
+	.get_status		= vduse_vdpa_get_status,
+	.set_status		= vduse_vdpa_set_status,
+	.get_config		= vduse_vdpa_get_config,
+	.set_config		= vduse_vdpa_set_config,
+	.free			= vduse_vdpa_free,
+};
+
+static dma_addr_t vduse_dev_map_page(struct device *dev, struct page *page,
+					unsigned long offset, size_t size,
+					enum dma_data_direction dir,
+					unsigned long attrs)
+{
+	struct vduse_dev *vdev = dev_to_vduse(dev);
+	struct vduse_iova_domain *domain = vdev->domain;
+	unsigned long iova = vduse_domain_alloc_iova(domain, size,
+							TYPE_BOUNCE_MAP);
+	unsigned long orig = (unsigned long)page_address(page) + offset;
+
+	if (!iova)
+		return DMA_MAPPING_ERROR;
+
+	if (vduse_domain_add_mapping(domain, iova, orig, size, dir)) {
+		vduse_domain_free_iova(domain, iova, size);
+		return DMA_MAPPING_ERROR;
+	}
+
+	if (dir == DMA_TO_DEVICE)
+		vduse_domain_bounce(domain, iova, orig, size, dir);
+
+	return (dma_addr_t)iova;
+}
+
+static void vduse_dev_unmap_page(struct device *dev, dma_addr_t dma_addr,
+				size_t size, enum dma_data_direction dir,
+				unsigned long attrs)
+{
+	struct vduse_dev *vdev = dev_to_vduse(dev);
+	struct vduse_iova_domain *domain = vdev->domain;
+	unsigned long iova = (unsigned long)dma_addr;
+	struct vduse_iova_map *map = vduse_domain_get_mapping(domain,
+							iova, size);
+	if (WARN_ON(!map))
+		return;
+
+	if (dir == DMA_FROM_DEVICE)
+		vduse_domain_bounce(domain, iova, map->orig, size, dir);
+	vduse_domain_remove_mapping(domain, map);
+	vduse_domain_free_iova(domain, iova, size);
+	kfree(map);
+}
+
+static void *vduse_dev_alloc_coherent(struct device *dev, size_t size,
+					dma_addr_t *dma_addr, gfp_t flag,
+					unsigned long attrs)
+{
+	struct vduse_dev *vdev = dev_to_vduse(dev);
+	struct vduse_iova_domain *domain = vdev->domain;
+	unsigned long iova = vduse_domain_alloc_iova(domain, size,
+							TYPE_DIRECT_MAP);
+	void *orig = alloc_pages_exact(size, flag);
+
+	if (!iova || !orig)
+		goto err;
+
+	if (vduse_domain_add_mapping(domain, iova,
+				(unsigned long)orig, size, DMA_BIDIRECTIONAL))
+		goto err;
+
+	*dma_addr = (dma_addr_t)iova;
+
+	return orig;
+err:
+	*dma_addr = DMA_MAPPING_ERROR;
+	if (orig)
+		free_pages_exact(orig, size);
+	if (iova)
+		vduse_domain_free_iova(domain, iova, size);
+
+	return NULL;
+}
+
+static void vduse_dev_free_coherent(struct device *dev, size_t size,
+					void *vaddr, dma_addr_t dma_addr,
+					unsigned long attrs)
+{
+	struct vduse_dev *vdev = dev_to_vduse(dev);
+	struct vduse_iova_domain *domain = vdev->domain;
+	unsigned long iova = (unsigned long)dma_addr;
+	struct vduse_iova_map *map = vduse_domain_get_mapping(domain,
+							iova, size);
+	if (WARN_ON(!map))
+		return;
+
+	vduse_domain_remove_mapping(domain, map);
+	vduse_domain_unmap(domain, map->iova.start, PAGE_ALIGN(map->size));
+	free_pages_exact((void *)map->orig, map->size);
+	vduse_domain_free_iova(domain, map->iova.start, map->size);
+	kfree(map);
+}
+
+static const struct dma_map_ops vduse_dev_dma_ops = {
+	.map_page = vduse_dev_map_page,
+	.unmap_page = vduse_dev_unmap_page,
+	.alloc = vduse_dev_alloc_coherent,
+	.free = vduse_dev_free_coherent,
+};
+
+static void vduse_dev_mmap_open(struct vm_area_struct *vma)
+{
+	struct vduse_iova_domain *domain = vma->vm_private_data;
+
+	if (!vduse_domain_add_vma(domain, vma))
+		return;
+
+	vma->vm_private_data = NULL;
+}
+
+static void vduse_dev_mmap_close(struct vm_area_struct *vma)
+{
+	struct vduse_iova_domain *domain = vma->vm_private_data;
+
+	if (!domain)
+		return;
+
+	vduse_domain_remove_vma(domain, vma);
+}
+
+static int vduse_dev_mmap_split(struct vm_area_struct *vma, unsigned long addr)
+{
+	return -EPERM;
+}
+
+static vm_fault_t vduse_dev_mmap_fault(struct vm_fault *vmf)
+{
+	struct vm_area_struct *vma = vmf->vma;
+	struct vduse_iova_domain *domain = vma->vm_private_data;
+	unsigned long iova = vmf->address - vma->vm_start;
+	int ret;
+
+	if (!domain)
+		return VM_FAULT_SIGBUS;
+
+	if (vduse_domain_is_direct_map(domain, iova))
+		ret = vduse_domain_direct_map(domain, vma, iova);
+	else
+		ret = vduse_domain_bounce_map(domain, vma, iova);
+
+	if (ret == -ENOMEM)
+		return VM_FAULT_OOM;
+
+	return (ret == 0) ? VM_FAULT_NOPAGE : VM_FAULT_SIGBUS;
+}
+
+static const struct vm_operations_struct vduse_dev_mmap_ops = {
+	.open = vduse_dev_mmap_open,
+	.close = vduse_dev_mmap_close,
+	.split = vduse_dev_mmap_split,
+	.fault = vduse_dev_mmap_fault,
+};
+
+static int vduse_dev_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct vduse_dev *dev = file->private_data;
+	struct vduse_iova_domain *domain = dev->domain;
+	unsigned long size = vma->vm_end - vma->vm_start;
+	int ret;
+
+	if (domain->size != size || vma->vm_pgoff)
+		return -EINVAL;
+
+	ret = vduse_domain_add_vma(domain, vma);
+	if (ret)
+		return ret;
+
+	vma->vm_flags |= VM_MIXEDMAP | VM_DONTCOPY |
+				VM_DONTDUMP | VM_DONTEXPAND;
+	vma->vm_private_data = domain;
+	vma->vm_ops = &vduse_dev_mmap_ops;
+
+	return 0;
+}
+
+static void vduse_vdpa_start_work(struct work_struct *work)
+{
+	struct vduse_vdpa *vdev = container_of(work,
+					struct vduse_vdpa, start_work);
+	struct vduse_dev *dev = vdev->dev;
+
+	if (vdpa_register_device(&vdev->vdpa)) {
+		dev->vdev = NULL;
+		put_device(&vdev->vdpa.dev);
+		wake_up_all(&dev->waitq);
+	}
+}
+
+static void vduse_vdpa_stop_work(struct work_struct *work)
+{
+	struct vduse_vdpa *vdev = container_of(work,
+					struct vduse_vdpa, stop_work);
+	vdpa_unregister_device(&vdev->vdpa);
+}
+
+static int vduse_dev_start(struct vduse_dev *dev)
+{
+	struct vduse_vdpa *vdev = dev->vdev;
+
+	if (vdev)
+		return -EBUSY;
+
+	vdev = vdpa_alloc_device(struct vduse_vdpa, vdpa, NULL,
+				&vduse_vdpa_config_ops, dev->vq_num);
+	if (!vdev)
+		return -ENOMEM;
+
+	dev->vdev = vdev;
+	vdev->dev = dev;
+	vdev->vdpa.dev.coherent_dma_mask = DMA_BIT_MASK(64);
+	set_dma_ops(&vdev->vdpa.dev, &vduse_dev_dma_ops);
+	vdev->vdpa.dma_dev = &vdev->vdpa.dev;
+
+	INIT_WORK(&vdev->start_work, vduse_vdpa_start_work);
+	queue_work(vduse_vdpa_wq, &vdev->start_work);
+
+	return 0;
+}
+
+static int vduse_dev_stop(struct vduse_dev *dev)
+{
+	struct vduse_vdpa *vdev = dev->vdev;
+
+	if (!vdev)
+		return -EPERM;
+
+	if (vdev->stopping)
+		return -EBUSY;
+
+	vdev->stopping = true;
+	INIT_WORK(&vdev->stop_work, vduse_vdpa_stop_work);
+	queue_work(vduse_vdpa_wq, &vdev->stop_work);
+
+	return 0;
+}
+
+static long vduse_dev_ioctl(struct file *file, unsigned int cmd,
+			unsigned long arg)
+{
+	struct vduse_dev *dev = file->private_data;
+	void __user *argp = (void __user *)arg;
+	int ret;
+
+	mutex_lock(&dev->lock);
+	switch (cmd) {
+	case VDUSE_DEV_START:
+		ret = vduse_dev_start(dev);
+		break;
+	case VDUSE_DEV_STOP:
+		ret = vduse_dev_stop(dev);
+		break;
+	case VDUSE_VQ_SETUP_KICKFD: {
+		struct vduse_vq_eventfd eventfd;
+
+		ret = -EFAULT;
+		if (copy_from_user(&eventfd, argp, sizeof(eventfd)))
+			break;
+
+		ret = vduse_kickfd_setup(dev, &eventfd);
+		break;
+	}
+	case VDUSE_VQ_SETUP_IRQFD: {
+		struct vduse_vq_eventfd eventfd;
+
+		ret = -EFAULT;
+		if (copy_from_user(&eventfd, argp, sizeof(eventfd)))
+			break;
+
+		ret = vduse_virqfd_setup(dev, &eventfd);
+		break;
+	}
+	}
+	mutex_unlock(&dev->lock);
+
+	return ret;
+}
+
+static int vduse_dev_release(struct inode *inode, struct file *file)
+{
+	struct vduse_dev *dev = file->private_data;
+	struct vduse_dev_msg *msg;
+
+	while ((msg = vduse_dev_dequeue_msg(dev, &dev->recv_list)))
+		vduse_dev_enqueue_msg(dev, msg, &dev->send_list);
+
+	dev->connected = false;
+
+	return 0;
+}
+
+static const struct file_operations vduse_dev_fops = {
+	.owner		= THIS_MODULE,
+	.release	= vduse_dev_release,
+	.read_iter	= vduse_dev_read_iter,
+	.write_iter	= vduse_dev_write_iter,
+	.poll		= vduse_dev_poll,
+	.mmap		= vduse_dev_mmap,
+	.unlocked_ioctl	= vduse_dev_ioctl,
+	.compat_ioctl	= compat_ptr_ioctl,
+	.llseek		= noop_llseek,
+};
+
+static struct vduse_dev *vduse_dev_create(void)
+{
+	struct vduse_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+
+	if (!dev)
+		return NULL;
+
+	mutex_init(&dev->lock);
+	spin_lock_init(&dev->msg_lock);
+	INIT_LIST_HEAD(&dev->send_list);
+	INIT_LIST_HEAD(&dev->recv_list);
+	atomic64_set(&dev->msg_unique, 0);
+	init_waitqueue_head(&dev->waitq);
+
+	return dev;
+}
+
+static void vduse_dev_destroy(struct vduse_dev *dev)
+{
+	mutex_destroy(&dev->lock);
+	kfree(dev);
+}
+
+static struct vduse_dev *vduse_find_dev(u32 id)
+{
+	struct vduse_dev *tmp, *dev = NULL;
+
+	list_for_each_entry(tmp, &vduse_devs, list) {
+		if (tmp->id == id) {
+			dev = tmp;
+			break;
+		}
+	}
+	return dev;
+}
+
+static int vduse_get_dev(u32 id)
+{
+	int fd;
+	char name[64];
+	struct vduse_dev *dev = vduse_find_dev(id);
+
+	if (!dev)
+		return -EINVAL;
+
+	if (dev->connected)
+		return -EBUSY;
+
+	snprintf(name, sizeof(name), "vduse-dev:%u", dev->id);
+	fd = anon_inode_getfd(name, &vduse_dev_fops, dev, O_RDWR | O_CLOEXEC);
+	if (fd < 0)
+		return fd;
+
+	dev->connected = true;
+
+	return fd;
+}
+
+static int vduse_destroy_dev(u32 id)
+{
+	struct vduse_dev *dev = vduse_find_dev(id);
+
+	if (!dev)
+		return -EINVAL;
+
+	if (dev->connected || dev->vdev)
+		return -EBUSY;
+
+	list_del(&dev->list);
+	kfree(dev->vqs);
+	vduse_iova_domain_destroy(dev->domain);
+	vduse_dev_destroy(dev);
+
+	return 0;
+}
+
+static int vduse_create_dev(struct vduse_dev_config *config)
+{
+	int i, fd;
+	struct vduse_dev *dev;
+	char name[64];
+
+	if (vduse_find_dev(config->id))
+		return -EEXIST;
+
+	dev = vduse_dev_create();
+	if (!dev)
+		return -ENOMEM;
+
+	dev->id = config->id;
+	dev->device_id = config->device_id;
+	dev->vendor_id = config->vendor_id;
+	dev->domain = vduse_iova_domain_create(config->iova_size);
+	if (!dev->domain)
+		goto err_domain;
+
+	dev->vq_align = config->vq_align;
+	dev->vq_size_max = config->vq_size_max;
+	dev->vq_num = config->vq_num;
+	dev->vqs = kcalloc(dev->vq_num, sizeof(*dev->vqs), GFP_KERNEL);
+	if (!dev->vqs)
+		goto err_vqs;
+
+	for (i = 0; i < dev->vq_num; i++) {
+		dev->vqs[i].index = i;
+		spin_lock_init(&dev->vqs[i].kick_lock);
+		spin_lock_init(&dev->vqs[i].irq_lock);
+	}
+
+	snprintf(name, sizeof(name), "vduse-dev:%u", config->id);
+	fd = anon_inode_getfd(name, &vduse_dev_fops, dev, O_RDWR | O_CLOEXEC);
+	if (fd < 0)
+		goto err_fd;
+
+	dev->connected = true;
+	list_add(&dev->list, &vduse_devs);
+
+	return fd;
+err_fd:
+	kfree(dev->vqs);
+err_vqs:
+	vduse_iova_domain_destroy(dev->domain);
+err_domain:
+	vduse_dev_destroy(dev);
+	return fd;
+}
+
+static long vduse_ioctl(struct file *file, unsigned int cmd,
+			unsigned long arg)
+{
+	int ret;
+	void __user *argp = (void __user *)arg;
+
+	mutex_lock(&vduse_lock);
+	switch (cmd) {
+	case VDUSE_CREATE_DEV: {
+		struct vduse_dev_config config;
+
+		ret = -EFAULT;
+		if (copy_from_user(&config, argp, sizeof(config)))
+			break;
+
+		ret = vduse_create_dev(&config);
+		break;
+	}
+	case VDUSE_GET_DEV:
+		ret = vduse_get_dev(arg);
+		break;
+	case VDUSE_DESTROY_DEV:
+		ret = vduse_destroy_dev(arg);
+		break;
+	default:
+		ret = -EINVAL;
+		break;
+	}
+	mutex_unlock(&vduse_lock);
+
+	return ret;
+}
+
+static const struct file_operations vduse_fops = {
+	.owner		= THIS_MODULE,
+	.unlocked_ioctl	= vduse_ioctl,
+	.compat_ioctl	= compat_ptr_ioctl,
+	.llseek		= noop_llseek,
+};
+
+static struct miscdevice vduse_misc = {
+	.fops = &vduse_fops,
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "vduse",
+};
+
+static int vduse_init(void)
+{
+	int ret;
+
+	ret = misc_register(&vduse_misc);
+	if (ret)
+		return ret;
+
+	ret = -ENOMEM;
+	vduse_vdpa_wq = alloc_workqueue("vduse-vdpa", WQ_UNBOUND, 1);
+	if (!vduse_vdpa_wq)
+		goto err_vdpa_wq;
+
+	ret = vduse_virqfd_init();
+	if (ret)
+		goto err_irqfd;
+
+	return 0;
+err_irqfd:
+	destroy_workqueue(vduse_vdpa_wq);
+err_vdpa_wq:
+	misc_deregister(&vduse_misc);
+	return ret;
+}
+module_init(vduse_init);
+
+static void vduse_exit(void)
+{
+	misc_deregister(&vduse_misc);
+	destroy_workqueue(vduse_vdpa_wq);
+	vduse_virqfd_exit();
+}
+module_exit(vduse_exit);
+
+MODULE_VERSION(DRV_VERSION);
+MODULE_LICENSE(DRV_LICENSE);
+MODULE_AUTHOR(DRV_AUTHOR);
+MODULE_DESCRIPTION(DRV_DESC);
diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
new file mode 100644
index 000000000000..855d2116b3a6
--- /dev/null
+++ b/include/uapi/linux/vduse.h
@@ -0,0 +1,85 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _UAPI_VDUSE_H_
+#define _UAPI_VDUSE_H_
+
+#include <linux/types.h>
+
+#define VDUSE_CONFIG_DATA_LEN	8
+
+enum vduse_req_type {
+	VDUSE_SET_VQ_STATE,
+	VDUSE_SET_FEATURES,
+	VDUSE_GET_FEATURES,
+	VDUSE_SET_STATUS,
+	VDUSE_GET_STATUS,
+	VDUSE_SET_CONFIG,
+	VDUSE_GET_CONFIG,
+};
+
+struct vduse_vq_state {
+	__u32 index;
+	__u32 num;
+	__u64 desc_addr;
+	__u64 driver_addr;
+	__u64 device_addr;
+	__u8 ready;
+};
+
+struct vduse_dev_config_data {
+	__u32 offset;
+	__u32 len;
+	__u8 data[VDUSE_CONFIG_DATA_LEN];
+};
+
+struct vduse_dev_request {
+	__u32 type;
+	__u32 unique;
+	__u32 flags;
+	__u32 size;
+	union {
+		struct vduse_vq_state vq_state;
+		struct vduse_dev_config_data config;
+		__u64 features;
+		__u8 status;
+	};
+};
+
+struct vduse_dev_response {
+	__u32 unique;
+	__s32 result;
+	union {
+		struct vduse_dev_config_data config;
+		__u64 features;
+		__u8 status;
+	};
+};
+
+/* ioctl */
+
+struct vduse_dev_config {
+	__u32 id;
+	__u32 vendor_id;
+	__u32 device_id;
+	__u64 iova_size;
+	__u16 vq_num;
+	__u16 vq_size_max;
+	__u32 vq_align;
+};
+
+struct vduse_vq_eventfd {
+	__u32 index;
+	__u32 fd;
+};
+
+#define VDUSE_BASE	'V'
+
+#define VDUSE_CREATE_DEV	_IOW(VDUSE_BASE, 0x01, struct vduse_dev_config)
+#define VDUSE_GET_DEV		_IO(VDUSE_BASE, 0x02)
+#define VDUSE_DESTROY_DEV	_IO(VDUSE_BASE, 0x03)
+
+#define VDUSE_DEV_START		_IO(VDUSE_BASE, 0x04)
+#define VDUSE_DEV_STOP		_IO(VDUSE_BASE, 0x05)
+#define VDUSE_VQ_SETUP_KICKFD	_IOW(VDUSE_BASE, 0x06, struct vduse_vq_eventfd)
+#define VDUSE_VQ_SETUP_IRQFD	_IOW(VDUSE_BASE, 0x07, struct vduse_vq_eventfd)
+
+#endif /* _UAPI_VDUSE_H_ */
-- 
2.25.1