Re: [RFC v3 08/11] vduse: Introduce VDUSE - vDPA Device in Userspace

[Jason Wang <jasowang@redhat.com>]

On 2021/1/19 下午1:07, Xie Yongji wrote:
> 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 config operation from vdpa bus driver
> to userspace. Userspace can use read()/write() to receive/reply
> those control messages.
>
> In the data path, VDUSE_IOTLB_GET_FD ioctl will be used to get
> the file descriptors referring to vDPA device's iova regions. Then
> userspace can use mmap() to access those iova regions. Besides,
> the eventfd mechanism is used to trigger interrupt callbacks and
> receive virtqueue kicks in userspace.
>
> Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> ---
>   Documentation/driver-api/vduse.rst                 |   85 ++
>   Documentation/userspace-api/ioctl/ioctl-number.rst |    1 +
>   drivers/vdpa/Kconfig                               |    7 +
>   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               |  426 +++++++
>   drivers/vdpa/vdpa_user/iova_domain.h               |   68 ++
>   drivers/vdpa/vdpa_user/vduse.h                     |   62 +
>   drivers/vdpa/vdpa_user/vduse_dev.c                 | 1217 ++++++++++++++++++++
>   include/uapi/linux/vdpa.h                          |    1 +
>   include/uapi/linux/vduse.h                         |  125 ++
>   13 files changed, 2267 insertions(+)
>   create mode 100644 Documentation/driver-api/vduse.rst
>   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/Documentation/driver-api/vduse.rst b/Documentation/driver-api/vduse.rst
> new file mode 100644
> index 000000000000..9418a7f6646b
> --- /dev/null
> +++ b/Documentation/driver-api/vduse.rst
> @@ -0,0 +1,85 @@
> +==================================
> +VDUSE - "vDPA Device in Userspace"
> +==================================
> +
> +vDPA (virtio data path acceleration) device is a device that uses a
> +datapath which complies with the virtio specifications with vendor
> +specific control path. vDPA devices can be both physically located on
> +the hardware or emulated by software. VDUSE is a framework that makes it
> +possible to implement software-emulated vDPA devices in userspace.
> +
> +How VDUSE works
> +------------
> +Each userspace vDPA device is created by the VDUSE_CREATE_DEV ioctl on
> +the VDUSE character device (/dev/vduse). Then a file descriptor pointing
> +to the new resources will be returned, which can be used to implement the
> +userspace vDPA device's control path and data path.
> +
> +To implement control path, the read/write operations to the file descriptor
> +will be used to receive/reply the control messages from/to VDUSE driver.


It's better to document the protocol here. E.g the identifier stuffs.


> +Those control messages are mostly based on the vdpa_config_ops which defines
> +a unified interface to control different types of vDPA device.
> +
> +The following types of messages are provided by the VDUSE framework now:
> +
> +- VDUSE_SET_VQ_ADDR: Set the addresses of the different aspects of virtqueue.


"Set the vring address of a virtqueue" might be better here.


> +
> +- VDUSE_SET_VQ_NUM: Set the size of virtqueue
> +
> +- VDUSE_SET_VQ_READY: Set ready status of virtqueue
> +
> +- VDUSE_GET_VQ_READY: Get ready status of virtqueue
> +
> +- VDUSE_SET_VQ_STATE: Set the state (last_avail_idx) for virtqueue
> +
> +- VDUSE_GET_VQ_STATE: Get the state (last_avail_idx) for virtqueue


It's better not to mention layout specific stuffs here (last_avail_idx). 
Consider we should support packed virtqueue in the future.


> +
> +- VDUSE_SET_FEATURES: Set virtio features supported by the driver
> +
> +- VDUSE_GET_FEATURES: Get virtio features supported by the device
> +
> +- VDUSE_SET_STATUS: Set the device status
> +
> +- VDUSE_GET_STATUS: Get the device status
> +
> +- VDUSE_SET_CONFIG: Write to device specific configuration space
> +
> +- VDUSE_GET_CONFIG: Read from device specific configuration space
> +
> +- VDUSE_UPDATE_IOTLB: Notify userspace to update the memory mapping in device IOTLB
> +
> +Please see include/linux/vdpa.h for details.
> +
> +In the data path, vDPA device's iova regions will be mapped into userspace with
> +the help of VDUSE_IOTLB_GET_FD ioctl on the userspace vDPA device fd:
> +
> +- VDUSE_IOTLB_GET_FD: get the file descriptor to iova region. Userspace can
> +  access this iova region by passing the fd to mmap(2).
> +
> +Besides, the eventfd mechanism is used to trigger interrupt callbacks and
> +receive virtqueue kicks in userspace. The following ioctls on the userspace
> +vDPA device fd are provided to support that:
> +
> +- VDUSE_VQ_SETUP_KICKFD: set the kickfd for virtqueue, this eventfd is used
> +  by VDUSE driver to notify userspace to consume the vring.
> +
> +- VDUSE_VQ_SETUP_IRQFD: set the irqfd for virtqueue, this eventfd is used
> +  by userspace to notify VDUSE driver to trigger interrupt callbacks.
> +
> +MMU-based IOMMU Driver
> +----------------------
> +In virtio-vdpa case, VDUSE framework implements a MMU-based on-chip IOMMU
> +driver to support mapping the kernel dma buffer into the userspace iova
> +region dynamically.
> +
> +The basic idea behind this driver is treating MMU (VA->PA) as IOMMU (IOVA->PA).
> +The driver will set up MMU mapping instead of IOMMU mapping for the DMA transfer
> +so that the userspace process is able to use its virtual address to access
> +the dma buffer in kernel.
> +
> +And to avoid security issue, a bounce-buffering mechanism is introduced to
> +prevent userspace accessing the original buffer directly which may contain other
> +kernel data. During the mapping, unmapping, the driver will copy the data from
> +the original buffer to the bounce buffer and back, depending on the direction of
> +the transfer. And the bounce-buffer addresses will be mapped into the user address
> +space instead of the original one.
> diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
> index a4c75a28c839..71722e6f8f23 100644
> --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> @@ -300,6 +300,7 @@ Code  Seq#    Include File                                           Comments
>   'z'   10-4F  drivers/s390/crypto/zcrypt_api.h                        conflict!
>   '|'   00-7F  linux/media.h
>   0x80  00-1F  linux/fb.h
> +0x81  00-1F  linux/vduse.h
>   0x89  00-06  arch/x86/include/asm/sockios.h
>   0x89  0B-DF  linux/sockios.h
>   0x89  E0-EF  linux/sockios.h                                         SIOCPROTOPRIVATE range
> diff --git a/drivers/vdpa/Kconfig b/drivers/vdpa/Kconfig
> index 4be7be39be26..667354309bf4 100644
> --- a/drivers/vdpa/Kconfig
> +++ b/drivers/vdpa/Kconfig
> @@ -21,6 +21,13 @@ 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


Need select VHOST_IOTLB.


> +	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..cdfef8e9f9d6
> --- /dev/null
> +++ b/drivers/vdpa/vdpa_user/iova_domain.c
> @@ -0,0 +1,426 @@
> +// 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/slab.h>
> +#include <linux/file.h>
> +#include <linux/anon_inodes.h>
> +
> +#include "iova_domain.h"
> +
> +#define IOVA_START_PFN 1
> +#define IOVA_ALLOC_ORDER 12
> +#define IOVA_ALLOC_SIZE (1 << IOVA_ALLOC_ORDER)


Can this work for all archs (e.g why not use PAGE_SIZE)?


> +
> +#define CONSISTENT_DMA_SIZE (1024 * 1024 * 1024)
> +
> +static inline struct page *
> +vduse_domain_get_bounce_page(struct vduse_iova_domain *domain,
> +				unsigned long iova)
> +{
> +	unsigned long index = iova >> PAGE_SHIFT;
> +
> +	return domain->bounce_pages[index];
> +}
> +
> +static inline void
> +vduse_domain_set_bounce_page(struct vduse_iova_domain *domain,
> +				unsigned long iova, struct page *page)
> +{
> +	unsigned long index = iova >> PAGE_SHIFT;
> +
> +	domain->bounce_pages[index] = page;
> +}
> +
> +static struct vduse_iova_map *
> +vduse_domain_alloc_iova_map(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 NULL;
> +
> +	map->iova.start = iova;
> +	map->iova.last = iova + size - 1;
> +	map->orig = orig;
> +	map->size = size;
> +	map->dir = dir;
> +
> +	return map;
> +}
> +
> +static struct page *
> +vduse_domain_get_mapping_page(struct vduse_iova_domain *domain,
> +				unsigned long iova)
> +{
> +	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 = NULL;
> +
> +	spin_lock(&domain->map_lock);
> +	node = interval_tree_iter_first(&domain->mappings, start, last);
> +	if (!node)
> +		goto out;
> +
> +	map = container_of(node, struct vduse_iova_map, iova);
> +	page = virt_to_page(map->orig + iova - map->iova.start);
> +	get_page(page);
> +out:
> +	spin_unlock(&domain->map_lock);
> +
> +	return page;
> +}
> +
> +static struct page *
> +vduse_domain_alloc_bounce_page(struct vduse_iova_domain *domain,
> +				unsigned long iova)
> +{
> +	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 = NULL, *new_page = alloc_page(GFP_KERNEL);
> +
> +	if (!new_page)
> +		return NULL;
> +
> +	spin_lock(&domain->map_lock);
> +	node = interval_tree_iter_first(&domain->mappings, start, last);
> +	if (!node) {
> +		__free_page(new_page);
> +		goto out;
> +	}
> +	page = vduse_domain_get_bounce_page(domain, iova);
> +	if (page) {
> +		get_page(page);
> +		__free_page(new_page);


Let's delay the allocation of new_page until it is really required.


> +		goto out;
> +	}
> +	vduse_domain_set_bounce_page(domain, iova, new_page);
> +	get_page(new_page);
> +	page = new_page;
> +
> +	while (node) {


I may miss something but which case should we do the loop here?


> +		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);
> +	}
> +out:
> +	spin_unlock(&domain->map_lock);
> +
> +	return page;
> +}
> +
> +static void
> +vduse_domain_free_bounce_pages(struct vduse_iova_domain *domain,
> +				unsigned long iova, size_t size)
> +{
> +	struct page *page;
> +	struct interval_tree_node *node;
> +	unsigned long last = iova + size - 1;
> +
> +	spin_lock(&domain->map_lock);
> +	node = interval_tree_iter_first(&domain->mappings, iova, last);
> +	if (WARN_ON(node))
> +		goto out;
> +
> +	while (size > 0) {
> +		page = vduse_domain_get_bounce_page(domain, iova);
> +		if (page) {
> +			vduse_domain_set_bounce_page(domain, iova, NULL);
> +			__free_page(page);
> +		}
> +		size -= PAGE_SIZE;
> +		iova += PAGE_SIZE;
> +	}
> +out:
> +	spin_unlock(&domain->map_lock);
> +}
> +
> +static 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;
> +
> +		WARN_ON(!p && dir == DMA_FROM_DEVICE);
> +
> +		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;
> +	}
> +}
> +
> +static unsigned long vduse_domain_alloc_iova(struct iova_domain *iovad,
> +				unsigned long size, unsigned long limit)
> +{
> +	unsigned long shift = iova_shift(iovad);
> +	unsigned long iova_len = iova_align(iovad, size) >> shift;
> +	unsigned long iova_pfn;
> +
> +	if (iova_len < (1 << (IOVA_RANGE_CACHE_MAX_SIZE - 1)))
> +		iova_len = roundup_pow_of_two(iova_len);
> +	iova_pfn = alloc_iova_fast(iovad, iova_len, limit >> shift, true);
> +
> +	return iova_pfn << shift;
> +}
> +
> +static void vduse_domain_free_iova(struct iova_domain *iovad,
> +				unsigned long iova, size_t size)
> +{
> +	unsigned long shift = iova_shift(iovad);
> +	unsigned long iova_len = iova_align(iovad, size) >> shift;
> +
> +	free_iova_fast(iovad, iova >> shift, iova_len);
> +}
> +
> +dma_addr_t vduse_domain_map_page(struct vduse_iova_domain *domain,
> +				struct page *page, unsigned long offset,
> +				size_t size, enum dma_data_direction dir,
> +				unsigned long attrs)
> +{
> +	struct iova_domain *iovad = &domain->stream_iovad;
> +	unsigned long limit = domain->bounce_size - 1;
> +	unsigned long iova = vduse_domain_alloc_iova(iovad, size, limit);
> +	unsigned long orig = (unsigned long)page_address(page) + offset;
> +	struct vduse_iova_map *map;
> +
> +	if (!iova)
> +		return DMA_MAPPING_ERROR;
> +
> +	map = vduse_domain_alloc_iova_map(domain, iova, orig, size, dir);
> +	if (!map) {
> +		vduse_domain_free_iova(iovad, iova, size);
> +		return DMA_MAPPING_ERROR;
> +	}
> +
> +	spin_lock(&domain->map_lock);
> +	interval_tree_insert(&map->iova, &domain->mappings);
> +	spin_unlock(&domain->map_lock);
> +
> +	if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
> +		vduse_domain_bounce(domain, iova, orig, size, DMA_TO_DEVICE);
> +
> +	return (dma_addr_t)iova;
> +}
> +
> +void vduse_domain_unmap_page(struct vduse_iova_domain *domain,
> +			dma_addr_t dma_addr, size_t size,
> +			enum dma_data_direction dir, unsigned long attrs)
> +{
> +	struct iova_domain *iovad = &domain->stream_iovad;
> +	unsigned long iova = (unsigned long)dma_addr;
> +	struct interval_tree_node *node;
> +	struct vduse_iova_map *map;
> +
> +	spin_lock(&domain->map_lock);
> +	node = interval_tree_iter_first(&domain->mappings, iova, iova + 1);
> +	if (WARN_ON(!node)) {
> +		spin_unlock(&domain->map_lock);
> +		return;
> +	}
> +	interval_tree_remove(node, &domain->mappings);
> +	spin_unlock(&domain->map_lock);
> +
> +	map = container_of(node, struct vduse_iova_map, iova);
> +	if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)
> +		vduse_domain_bounce(domain, iova, map->orig,
> +					size, DMA_FROM_DEVICE);
> +	vduse_domain_free_iova(iovad, iova, size);
> +	kfree(map);
> +}
> +
> +void *vduse_domain_alloc_coherent(struct vduse_iova_domain *domain,
> +				size_t size, dma_addr_t *dma_addr,
> +				gfp_t flag, unsigned long attrs)
> +{
> +	struct iova_domain *iovad = &domain->consistent_iovad;
> +	unsigned long limit = domain->bounce_size + CONSISTENT_DMA_SIZE - 1;
> +	unsigned long iova = vduse_domain_alloc_iova(iovad, size, limit);
> +	void *orig = alloc_pages_exact(size, flag);
> +	struct vduse_iova_map *map;
> +
> +	if (!iova || !orig)
> +		goto err;
> +
> +	map = vduse_domain_alloc_iova_map(domain, iova, (unsigned long)orig,
> +					size, DMA_BIDIRECTIONAL);
> +	if (!map)
> +		goto err;
> +
> +	spin_lock(&domain->map_lock);
> +	interval_tree_insert(&map->iova, &domain->mappings);
> +	spin_unlock(&domain->map_lock);
> +	*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(iovad, iova, size);
> +
> +	return NULL;
> +}
> +
> +void vduse_domain_free_coherent(struct vduse_iova_domain *domain, size_t size,
> +				void *vaddr, dma_addr_t dma_addr,
> +				unsigned long attrs)
> +{
> +	struct iova_domain *iovad = &domain->consistent_iovad;
> +	unsigned long iova = (unsigned long)dma_addr;
> +	struct interval_tree_node *node;
> +	struct vduse_iova_map *map;
> +
> +	spin_lock(&domain->map_lock);
> +	node = interval_tree_iter_first(&domain->mappings, iova, iova + 1);
> +	if (WARN_ON(!node)) {
> +		spin_unlock(&domain->map_lock);
> +		return;
> +	}
> +	interval_tree_remove(node, &domain->mappings);
> +	spin_unlock(&domain->map_lock);
> +
> +	map = container_of(node, struct vduse_iova_map, iova);
> +	vduse_domain_free_iova(iovad, iova, size);
> +	free_pages_exact(vaddr, size);
> +	kfree(map);
> +}
> +
> +static vm_fault_t vduse_domain_mmap_fault(struct vm_fault *vmf)
> +{
> +	struct vduse_iova_domain *domain = vmf->vma->vm_private_data;
> +	unsigned long iova = vmf->pgoff << PAGE_SHIFT;
> +	struct page *page;
> +
> +	if (!domain)
> +		return VM_FAULT_SIGBUS;
> +
> +	if (iova < domain->bounce_size)
> +		page = vduse_domain_alloc_bounce_page(domain, iova);
> +	else
> +		page = vduse_domain_get_mapping_page(domain, iova);
> +
> +	if (!page)
> +		return VM_FAULT_SIGBUS;
> +
> +	vmf->page = page;
> +
> +	return 0;
> +}
> +
> +static const struct vm_operations_struct vduse_domain_mmap_ops = {
> +	.fault = vduse_domain_mmap_fault,
> +};
> +
> +static int vduse_domain_mmap(struct file *file, struct vm_area_struct *vma)
> +{
> +	struct vduse_iova_domain *domain = file->private_data;
> +
> +	vma->vm_flags |= VM_DONTCOPY | VM_DONTDUMP | VM_DONTEXPAND;
> +	vma->vm_private_data = domain;
> +	vma->vm_ops = &vduse_domain_mmap_ops;
> +
> +	return 0;
> +}
> +
> +static int vduse_domain_release(struct inode *inode, struct file *file)
> +{
> +	struct vduse_iova_domain *domain = file->private_data;
> +
> +	vduse_domain_free_bounce_pages(domain, 0, domain->bounce_size);
> +	put_iova_domain(&domain->stream_iovad);
> +	put_iova_domain(&domain->consistent_iovad);
> +	vfree(domain->bounce_pages);
> +	kfree(domain);
> +
> +	return 0;
> +}
> +
> +static const struct file_operations vduse_domain_fops = {
> +	.mmap = vduse_domain_mmap,
> +	.release = vduse_domain_release,
> +};


It's better to explain the reason for introducing a dedicated file for 
mmap() here.


> +
> +void vduse_domain_destroy(struct vduse_iova_domain *domain)
> +{
> +	fput(domain->file);
> +}
> +
> +struct vduse_iova_domain *vduse_domain_create(size_t bounce_size)
> +{
> +	struct vduse_iova_domain *domain;
> +	struct file *file;
> +	unsigned long bounce_pfns = PAGE_ALIGN(bounce_size) >> PAGE_SHIFT;
> +
> +	domain = kzalloc(sizeof(*domain), GFP_KERNEL);
> +	if (!domain)
> +		return NULL;
> +
> +	domain->bounce_size = PAGE_ALIGN(bounce_size);
> +	domain->bounce_pages = vzalloc(bounce_pfns * sizeof(struct page *));
> +	if (!domain->bounce_pages)
> +		goto err_page;
> +
> +	file = anon_inode_getfile("[vduse-domain]", &vduse_domain_fops,
> +				domain, O_RDWR);
> +	if (IS_ERR(file))
> +		goto err_file;
> +
> +	domain->file = file;
> +	spin_lock_init(&domain->map_lock);
> +	domain->mappings = RB_ROOT_CACHED;
> +	init_iova_domain(&domain->stream_iovad,
> +			IOVA_ALLOC_SIZE, IOVA_START_PFN);
> +	init_iova_domain(&domain->consistent_iovad,
> +			PAGE_SIZE, bounce_pfns);
> +
> +	return domain;
> +err_file:
> +	vfree(domain->bounce_pages);
> +err_page:
> +	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..cc61866acb56
> --- /dev/null
> +++ b/drivers/vdpa/vdpa_user/iova_domain.h
> @@ -0,0 +1,68 @@
> +/* 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/iova.h>
> +#include <linux/interval_tree.h>
> +#include <linux/dma-mapping.h>
> +
> +struct vduse_iova_map {
> +	struct interval_tree_node iova;
> +	unsigned long orig;


Need a better name, probably "va"?


> +	size_t size;
> +	enum dma_data_direction dir;
> +};
> +
> +struct vduse_iova_domain {
> +	struct iova_domain stream_iovad;
> +	struct iova_domain consistent_iovad;
> +	struct page **bounce_pages;
> +	size_t bounce_size;
> +	struct rb_root_cached mappings;


We had IOTLB, any reason for this extra mappings here?


> +	spinlock_t map_lock;
> +	struct file *file;
> +};
> +
> +static inline struct file *
> +vduse_domain_file(struct vduse_iova_domain *domain)
> +{
> +	return domain->file;
> +}
> +
> +static inline unsigned long
> +vduse_domain_get_offset(struct vduse_iova_domain *domain, unsigned long iova)
> +{
> +	return iova;
> +}
> +
> +dma_addr_t vduse_domain_map_page(struct vduse_iova_domain *domain,
> +				struct page *page, unsigned long offset,
> +				size_t size, enum dma_data_direction dir,
> +				unsigned long attrs);
> +
> +void vduse_domain_unmap_page(struct vduse_iova_domain *domain,
> +			dma_addr_t dma_addr, size_t size,
> +			enum dma_data_direction dir, unsigned long attrs);
> +
> +void *vduse_domain_alloc_coherent(struct vduse_iova_domain *domain,
> +				size_t size, dma_addr_t *dma_addr,
> +				gfp_t flag, unsigned long attrs);
> +
> +void vduse_domain_free_coherent(struct vduse_iova_domain *domain, size_t size,
> +				void *vaddr, dma_addr_t dma_addr,
> +				unsigned long attrs);
> +
> +void vduse_domain_destroy(struct vduse_iova_domain *domain);
> +
> +struct vduse_iova_domain *vduse_domain_create(size_t bounce_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..3566d229382e
> --- /dev/null
> +++ b/drivers/vdpa/vdpa_user/vduse.h
> @@ -0,0 +1,62 @@
> +/* 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;
> +	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 vduse_dev {
> +	struct vduse_vdpa *vdev;
> +	struct mutex lock;
> +	struct vduse_virtqueue *vqs;
> +	struct vduse_iova_domain *domain;
> +	struct vhost_iotlb *iommu;
> +	spinlock_t iommu_lock;
> +	atomic_t bounce_map;
> +	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..1cf759bc5914
> --- /dev/null
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -0,0 +1,1217 @@
> +// 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-map-ops.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/vdpa.h>
> +#include <uapi/linux/virtio_config.h>
> +#include <linux/mod_devicetable.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;


The reference count here will bring extra complexity. I think we can 
sync through msg_lock.



> +};
> +
> +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);


This looks not safe, let's use idr here.


> +	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);


This is uninterruptible wait, it means if the userspace forget to 
process the command, we will stuck here forever.


> +	/* coupled with smp_wmb() in vduse_dev_msg_complete() */
> +	smp_rmb();


Instead of using barriers, I wonder why not simply use msg lock here?


> +	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_num(struct vduse_dev *dev,
> +				struct vduse_virtqueue *vq, u32 num)
> +{
> +	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_SET_VQ_NUM);
> +
> +	msg->req.size = sizeof(struct vduse_vq_num);
> +	msg->req.vq_num.index = vq->index;
> +	msg->req.vq_num.num = num;
> +
> +	vduse_dev_msg_sync(dev, msg);
> +	vduse_dev_msg_put(msg);
> +}
> +
> +static int vduse_dev_set_vq_addr(struct vduse_dev *dev,
> +				struct vduse_virtqueue *vq, u64 desc_addr,
> +				u64 driver_addr, u64 device_addr)
> +{
> +	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_SET_VQ_ADDR);
> +	int ret;
> +
> +	msg->req.size = sizeof(struct vduse_vq_addr);
> +	msg->req.vq_addr.index = vq->index;
> +	msg->req.vq_addr.desc_addr = desc_addr;
> +	msg->req.vq_addr.driver_addr = driver_addr;
> +	msg->req.vq_addr.device_addr = device_addr;
> +
> +	ret = vduse_dev_msg_sync(dev, msg);
> +	vduse_dev_msg_put(msg);
> +
> +	return ret;
> +}
> +
> +static void vduse_dev_set_vq_ready(struct vduse_dev *dev,
> +				struct vduse_virtqueue *vq, bool ready)
> +{
> +	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_SET_VQ_READY);
> +
> +	msg->req.size = sizeof(struct vduse_vq_ready);
> +	msg->req.vq_ready.index = vq->index;
> +	msg->req.vq_ready.ready = ready;
> +
> +	vduse_dev_msg_sync(dev, msg);
> +	vduse_dev_msg_put(msg);
> +}
> +
> +static bool vduse_dev_get_vq_ready(struct vduse_dev *dev,
> +				   struct vduse_virtqueue *vq)
> +{
> +	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_GET_VQ_READY);
> +	bool ready;
> +
> +	msg->req.size = sizeof(struct vduse_vq_ready);
> +	msg->req.vq_ready.index = vq->index;
> +
> +	vduse_dev_msg_sync(dev, msg);
> +	ready = msg->resp.vq_ready.ready;
> +	vduse_dev_msg_put(msg);
> +
> +	return ready;
> +}
> +
> +static int vduse_dev_get_vq_state(struct vduse_dev *dev,
> +				struct vduse_virtqueue *vq,
> +				struct vdpa_vq_state *state)
> +{
> +	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_GET_VQ_STATE);
> +	int ret;
> +
> +	msg->req.size = sizeof(struct vduse_vq_state);
> +	msg->req.vq_state.index = vq->index;
> +
> +	ret = vduse_dev_msg_sync(dev, msg);
> +	state->avail_index = msg->resp.vq_state.avail_idx;
> +	vduse_dev_msg_put(msg);
> +
> +	return ret;
> +}
> +
> +static int vduse_dev_set_vq_state(struct vduse_dev *dev,
> +				struct vduse_virtqueue *vq,
> +				const struct vdpa_vq_state *state)
> +{
> +	struct vduse_dev_msg *msg = vduse_dev_new_msg(dev, VDUSE_SET_VQ_STATE);
> +	int ret;
> +
> +	msg->req.size = sizeof(struct vduse_vq_state);
> +	msg->req.vq_state.index = vq->index;
> +	msg->req.vq_state.avail_idx = state->avail_index;
> +
> +	ret = vduse_dev_msg_sync(dev, msg);
> +	vduse_dev_msg_put(msg);
> +
> +	return ret;
> +}
> +
> +static int vduse_dev_update_iotlb(struct vduse_dev *dev,
> +					u64 start, u64 last)
> +{
> +	struct vduse_dev_msg *msg;
> +	int ret;
> +
> +	if (last < start)
> +		return -EINVAL;
> +
> +	msg = vduse_dev_new_msg(dev, VDUSE_UPDATE_IOTLB);


This is actually a IOTLB invalidation. So let's rename the function and 
message type.


> +	msg->req.size = sizeof(struct vduse_iova_range);
> +	msg->req.iova.start = start;
> +	msg->req.iova.last = last;
> +
> +	ret = vduse_dev_msg_sync(dev, msg);
> +	vduse_dev_msg_put(msg);
> +
> +	return ret;
> +}
> +
> +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) {
> +		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,
> +					!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;
> +
> +	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);


So we had multiple types of requests/responses, is this better to 
introduce a queue based admin interface other than ioctl?


> +
> +	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 (!list_empty(&dev->send_list))
> +		mask |= EPOLLIN | EPOLLRDNORM;
> +
> +	return mask;
> +}
> +
> +static int vduse_iotlb_add_range(struct vduse_dev *dev,
> +				 u64 start, u64 last,
> +				 u64 addr, unsigned int perm,
> +				 struct file *file, u64 offset)
> +{
> +	struct vhost_iotlb_file *iotlb_file;
> +	int ret;
> +
> +	iotlb_file = kmalloc(sizeof(*iotlb_file), GFP_ATOMIC);
> +	if (!iotlb_file)
> +		return -ENOMEM;
> +
> +	iotlb_file->file = get_file(file);
> +	iotlb_file->offset = offset;
> +
> +	spin_lock(&dev->iommu_lock);
> +	ret = vhost_iotlb_add_range(dev->iommu, start, last,
> +					addr, perm, iotlb_file);
> +	spin_unlock(&dev->iommu_lock);
> +	if (ret) {
> +		fput(iotlb_file->file);
> +		kfree(iotlb_file);
> +		return ret;
> +	}
> +	return 0;
> +}
> +
> +static void vduse_iotlb_del_range(struct vduse_dev *dev, u64 start, u64 last)
> +{
> +	struct vhost_iotlb_file *iotlb_file;
> +	struct vhost_iotlb_map *map;
> +
> +	spin_lock(&dev->iommu_lock);
> +	while ((map = vhost_iotlb_itree_first(dev->iommu, start, last))) {
> +		iotlb_file = (struct vhost_iotlb_file *)map->opaque;
> +		fput(iotlb_file->file);
> +		kfree(iotlb_file);
> +		vhost_iotlb_map_free(dev->iommu, map);
> +	}
> +	spin_unlock(&dev->iommu_lock);
> +}
> +
> +static void vduse_dev_reset(struct vduse_dev *dev)
> +{
> +	int i;
> +
> +	atomic_set(&dev->bounce_map, 0);
> +	vduse_iotlb_del_range(dev, 0ULL, 0ULL - 1);
> +	vduse_dev_update_iotlb(dev, 0ULL, 0ULL - 1);


ULLONG_MAX please.


> +
> +	for (i = 0; i < dev->vq_num; i++) {
> +		struct vduse_virtqueue *vq = &dev->vqs[i];
> +
> +		spin_lock(&vq->irq_lock);
> +		vq->ready = false;
> +		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 *dev = vdpa_to_vduse(vdpa);
> +	struct vduse_virtqueue *vq = &dev->vqs[idx];
> +
> +	return vduse_dev_set_vq_addr(dev, vq, desc_area,
> +					driver_area, device_area);
> +}
> +
> +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];
> +
> +	vduse_dev_set_vq_num(dev, vq, 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];
> +
> +	vduse_dev_set_vq_ready(dev, vq, ready);
> +	vq->ready = ready;
> +}
> +
> +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];
> +
> +	vq->ready = vduse_dev_get_vq_ready(dev, vq);
> +
> +	return vq->ready;
> +}
> +
> +static int vduse_vdpa_set_vq_state(struct vdpa_device *vdpa, u16 idx,
> +				const struct vdpa_vq_state *state)
> +{
> +	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> +	struct vduse_virtqueue *vq = &dev->vqs[idx];
> +
> +	return vduse_dev_set_vq_state(dev, vq, state);
> +}
> +
> +static int vduse_vdpa_get_vq_state(struct vdpa_device *vdpa, u16 idx,
> +				struct vdpa_vq_state *state)
> +{
> +	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> +	struct vduse_virtqueue *vq = &dev->vqs[idx];
> +
> +	return vduse_dev_get_vq_state(dev, vq, state);
> +}
> +
> +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 */


If it's not hard, let's add this. Otherwise we need a per device feature 
blacklist to filter out all features that depends on 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);
> +	else
> +		vduse_dev_update_iotlb(dev, 0ULL, 0ULL - 1);


Any reason for such IOTLB invalidation here?


> +
> +	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 int vduse_vdpa_set_map(struct vdpa_device *vdpa,
> +				struct vhost_iotlb *iotlb)
> +{
> +	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> +	struct vhost_iotlb_map *map;
> +	struct vhost_iotlb_file *iotlb_file;
> +	u64 start = 0ULL, last = 0ULL - 1;
> +	int ret = 0;
> +
> +	vduse_iotlb_del_range(dev, start, last);
> +
> +	for (map = vhost_iotlb_itree_first(iotlb, start, last); map;
> +		map = vhost_iotlb_itree_next(map, start, last)) {
> +		if (!map->opaque)
> +			continue;


What will happen if we simply accept NULL opaque here?


> +
> +		iotlb_file = (struct vhost_iotlb_file *)map->opaque;
> +		ret = vduse_iotlb_add_range(dev, map->start, map->last,
> +					    map->addr, map->perm,
> +					    iotlb_file->file,
> +					    iotlb_file->offset);
> +		if (ret)
> +			break;
> +	}
> +	vduse_dev_update_iotlb(dev, start, last);
> +
> +	return ret;
> +}
> +
> +static void vduse_vdpa_free(struct vdpa_device *vdpa)
> +{
> +	struct vduse_dev *dev = vdpa_to_vduse(vdpa);
> +
> +	WARN_ON(!list_empty(&dev->send_list));
> +	WARN_ON(!list_empty(&dev->recv_list));
> +	dev->vdev = NULL;
> +}
> +
> +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,
> +	.set_vq_state		= vduse_vdpa_set_vq_state,
> +	.get_vq_state		= vduse_vdpa_get_vq_state,
> +	.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,
> +	.set_map		= vduse_vdpa_set_map,
> +	.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;
> +
> +	if (atomic_xchg(&vdev->bounce_map, 1) == 0 &&
> +		vduse_iotlb_add_range(vdev, 0, domain->bounce_size - 1,
> +				      0, VDUSE_ACCESS_RW,


Is this safe to use VDUSE_ACCESS_RW here, consider we might have device 
readonly mappings.


> +				      vduse_domain_file(domain),
> +				      vduse_domain_get_offset(domain, 0))) {
> +		atomic_set(&vdev->bounce_map, 0);
> +		return DMA_MAPPING_ERROR;
> +	}
> +
> +	return vduse_domain_map_page(domain, page, offset, size, dir, attrs);
> +}
> +
> +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;
> +
> +	return vduse_domain_unmap_page(domain, dma_addr, size, dir, attrs);
> +}
> +
> +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;
> +	void *addr;
> +
> +	*dma_addr = DMA_MAPPING_ERROR;
> +	addr = vduse_domain_alloc_coherent(domain, size,
> +				(dma_addr_t *)&iova, flag, attrs);
> +	if (!addr)
> +		return NULL;
> +
> +	if (vduse_iotlb_add_range(vdev, iova, iova + size - 1,
> +				  iova, VDUSE_ACCESS_RW,
> +				  vduse_domain_file(domain),
> +				  vduse_domain_get_offset(domain, iova))) {
> +		vduse_domain_free_coherent(domain, size, addr, iova, attrs);
> +		return NULL;
> +	}
> +	*dma_addr = (dma_addr_t)iova;
> +
> +	return addr;
> +}
> +
> +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 start = (unsigned long)dma_addr;
> +	unsigned long last = start + size - 1;
> +
> +	vduse_iotlb_del_range(vdev, start, last);
> +	vduse_dev_update_iotlb(vdev, start, last);
> +	vduse_domain_free_coherent(domain, size, vaddr, dma_addr, attrs);
> +}
> +
> +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 unsigned int perm_to_file_flags(u8 perm)
> +{
> +	unsigned int flags = 0;
> +
> +	switch (perm) {
> +	case VDUSE_ACCESS_WO:
> +		flags |= O_WRONLY;
> +		break;
> +	case VDUSE_ACCESS_RO:
> +		flags |= O_RDONLY;
> +		break;
> +	case VDUSE_ACCESS_RW:
> +		flags |= O_RDWR;
> +		break;
> +	default:
> +		WARN(1, "invalidate vhost IOTLB permission\n");
> +		break;
> +	}
> +
> +	return flags;
> +}
> +
> +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_IOTLB_GET_FD: {
> +		struct vduse_iotlb_entry entry;
> +		struct vhost_iotlb_map *map;
> +		struct vhost_iotlb_file *iotlb_file;
> +		struct file *f = NULL;
> +
> +		ret = -EFAULT;
> +		if (copy_from_user(&entry, argp, sizeof(entry)))
> +			break;
> +
> +		spin_lock(&dev->iommu_lock);
> +		map = vhost_iotlb_itree_first(dev->iommu, entry.start,
> +					      entry.last);
> +		if (map) {
> +			iotlb_file = (struct vhost_iotlb_file *)map->opaque;
> +			f = get_file(iotlb_file->file);
> +			entry.offset = iotlb_file->offset;
> +			entry.start = map->start;
> +			entry.last = map->last;
> +			entry.perm = map->perm;
> +		}
> +		spin_unlock(&dev->iommu_lock);
> +		if (!f) {
> +			ret = -EINVAL;
> +			break;
> +		}
> +		if (copy_to_user(argp, &entry, sizeof(entry))) {
> +			fput(f);
> +			ret = -EFAULT;
> +			break;
> +		}
> +		ret = get_unused_fd_flags(perm_to_file_flags(entry.perm));
> +		if (ret < 0) {
> +			fput(f);
> +			break;
> +		}
> +		fd_install(ret, f);
> +		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;
> +
> +	vduse_kickfd_release(dev);
> +	vduse_virqfd_release(dev);
> +	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,
> +	.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;
> +
> +	dev->iommu = vhost_iotlb_alloc(2048, 0);


Is 2048 sufficient here?


> +	if (!dev->iommu) {
> +		kfree(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);
> +	spin_lock_init(&dev->iommu_lock);
> +	atomic_set(&dev->bounce_map, 0);
> +
> +	init_waitqueue_head(&dev->waitq);
> +
> +	return dev;
> +}
> +
> +static void vduse_dev_destroy(struct vduse_dev *dev)
> +{
> +	vhost_iotlb_free(dev->iommu);
> +	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_destroy_dev(u32 id)
> +{
> +	struct vduse_dev *dev = vduse_find_dev(id);
> +
> +	if (!dev)
> +		return -EINVAL;
> +
> +	if (dev->vdev || dev->connected)
> +		return -EBUSY;
> +
> +	list_del(&dev->list);
> +	kfree(dev->vqs);
> +	vduse_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_domain_create(config->bounce_size);


Do we need a upper limit of bounce_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);


Any reason for closing on exec here?


> +	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_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_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 void vduse_parent_release(struct device *dev)
> +{
> +}
> +
> +static struct device vduse_parent = {
> +	.init_name = "vduse",
> +	.release = vduse_parent_release,
> +};
> +
> +static struct vdpa_parent_dev parent_dev;
> +
> +static int vduse_dev_add_vdpa(struct vduse_dev *dev, const char *name)
> +{
> +	struct vduse_vdpa *vdev = dev->vdev;
> +	int ret;
> +
> +	if (vdev)
> +		return -EEXIST;
> +
> +	vdev = vdpa_alloc_device(struct vduse_vdpa, vdpa, NULL,
> +				 &vduse_vdpa_config_ops,
> +				 dev->vq_num, name, true);
> +	if (!vdev)
> +		return -ENOMEM;
> +
> +	vdev->dev = dev;
> +	vdev->vdpa.dev.dma_mask = &vdev->vdpa.dev.coherent_dma_mask;
> +	ret = dma_set_mask_and_coherent(&vdev->vdpa.dev, DMA_BIT_MASK(64));
> +	if (ret)
> +		goto err;
> +
> +	set_dma_ops(&vdev->vdpa.dev, &vduse_dev_dma_ops);
> +	vdev->vdpa.dma_dev = &vdev->vdpa.dev;
> +	vdev->vdpa.pdev = &parent_dev;
> +
> +	ret = _vdpa_register_device(&vdev->vdpa);
> +	if (ret)
> +		goto err;
> +
> +	dev->vdev = vdev;
> +
> +	return 0;
> +err:
> +	put_device(&vdev->vdpa.dev);
> +	return ret;
> +}
> +
> +static struct vdpa_device *vdpa_dev_add(struct vdpa_parent_dev *pdev,
> +					const char *name, u32 device_id,
> +					struct nlattr **attrs)
> +{
> +	u32 vduse_id;
> +	struct vduse_dev *dev;
> +	int ret = -EINVAL;
> +
> +	if (!attrs[VDPA_ATTR_BACKEND_ID])
> +		return ERR_PTR(-EINVAL);
> +
> +	mutex_lock(&vduse_lock);
> +	vduse_id = nla_get_u32(attrs[VDPA_ATTR_BACKEND_ID]);


I wonder why not using name here?

And it looks to me it would be easier if we create a char device per 
vduse. This makes the device addressing more robust than passing id 
silently among processes.


> +	dev = vduse_find_dev(vduse_id);
> +	if (!dev)
> +		goto unlock;
> +
> +	if (dev->device_id != device_id)
> +		goto unlock;
> +
> +	ret = vduse_dev_add_vdpa(dev, name);
> +unlock:
> +	mutex_unlock(&vduse_lock);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	return &dev->vdev->vdpa;
> +}
> +
> +static void vdpa_dev_del(struct vdpa_parent_dev *pdev, struct vdpa_device *dev)
> +{
> +	_vdpa_unregister_device(dev);
> +}
> +
> +static const struct vdpa_dev_ops vdpa_dev_parent_ops = {
> +	.dev_add = vdpa_dev_add,
> +	.dev_del = vdpa_dev_del
> +};
> +
> +static struct virtio_device_id id_table[] = {
> +	{ VIRTIO_DEV_ANY_ID, VIRTIO_DEV_ANY_ID },
> +	{ 0 },
> +};
> +
> +static struct vdpa_parent_dev parent_dev = {
> +	.device = &vduse_parent,
> +	.id_table = id_table,
> +	.ops = &vdpa_dev_parent_ops,
> +};
> +
> +static int vduse_parentdev_init(void)
> +{
> +	int ret;
> +
> +	ret = device_register(&vduse_parent);
> +	if (ret)
> +		return ret;
> +
> +	ret = vdpa_parentdev_register(&parent_dev);
> +	if (ret)
> +		goto err;
> +
> +	return 0;
> +err:
> +	device_unregister(&vduse_parent);
> +	return ret;
> +}
> +
> +static void vduse_parentdev_exit(void)
> +{
> +	vdpa_parentdev_unregister(&parent_dev);
> +	device_unregister(&vduse_parent);
> +}
> +
> +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;
> +
> +	ret = vduse_parentdev_init();
> +	if (ret)
> +		goto err_parentdev;
> +
> +	return 0;
> +err_parentdev:
> +	vduse_virqfd_exit();
> +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();
> +	vduse_parentdev_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/vdpa.h b/include/uapi/linux/vdpa.h
> index bba8b83a94b5..a7a841e5ffc7 100644
> --- a/include/uapi/linux/vdpa.h
> +++ b/include/uapi/linux/vdpa.h
> @@ -33,6 +33,7 @@ enum vdpa_attr {
>   	VDPA_ATTR_DEV_VENDOR_ID,		/* u32 */
>   	VDPA_ATTR_DEV_MAX_VQS,			/* u32 */
>   	VDPA_ATTR_DEV_MAX_VQ_SIZE,		/* u16 */
> +	VDPA_ATTR_BACKEND_ID,			/* u32 */


As discussed, this needs more thought. But if necessary, we need a 
separate patch for this.


>   
>   	/* new attributes must be added above here */
>   	VDPA_ATTR_MAX,
> diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
> new file mode 100644
> index 000000000000..9fb555ddcfbd
> --- /dev/null
> +++ b/include/uapi/linux/vduse.h
> @@ -0,0 +1,125 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> +#ifndef _UAPI_VDUSE_H_
> +#define _UAPI_VDUSE_H_
> +
> +#include <linux/types.h>
> +
> +/* the control messages definition for read/write */
> +
> +#define VDUSE_CONFIG_DATA_LEN	256
> +
> +enum vduse_req_type {
> +	VDUSE_SET_VQ_NUM,
> +	VDUSE_SET_VQ_ADDR,
> +	VDUSE_SET_VQ_READY,
> +	VDUSE_GET_VQ_READY,
> +	VDUSE_SET_VQ_STATE,
> +	VDUSE_GET_VQ_STATE,
> +	VDUSE_SET_FEATURES,
> +	VDUSE_GET_FEATURES,
> +	VDUSE_SET_STATUS,
> +	VDUSE_GET_STATUS,
> +	VDUSE_SET_CONFIG,
> +	VDUSE_GET_CONFIG,
> +	VDUSE_UPDATE_IOTLB,
> +};
> +
> +struct vduse_vq_num {
> +	__u32 index;
> +	__u32 num;
> +};
> +
> +struct vduse_vq_addr {
> +	__u32 index;
> +	__u64 desc_addr;
> +	__u64 driver_addr;
> +	__u64 device_addr;
> +};
> +
> +struct vduse_vq_ready {
> +	__u32 index;
> +	__u8 ready;
> +};
> +
> +struct vduse_vq_state {
> +	__u32 index;
> +	__u16 avail_idx;
> +};
> +
> +struct vduse_dev_config_data {
> +	__u32 offset;
> +	__u32 len;
> +	__u8 data[VDUSE_CONFIG_DATA_LEN];


This no guarantee that 256 is sufficient here.


> +};
> +
> +struct vduse_iova_range {
> +	__u64 start;
> +	__u64 last;
> +};
> +
> +struct vduse_dev_request {
> +	__u32 type; /* request type */
> +	__u32 unique; /* request id */
> +	__u32 flags; /* request flags */


Seems unused in this series.


> +	__u32 size; /* the payload size */


Unused.


> +	union {
> +		struct vduse_vq_num vq_num; /* virtqueue num */
> +		struct vduse_vq_addr vq_addr; /* virtqueue address */
> +		struct vduse_vq_ready vq_ready; /* virtqueue ready status */
> +		struct vduse_vq_state vq_state; /* virtqueue state */
> +		struct vduse_dev_config_data config; /* virtio device config space */
> +		struct vduse_iova_range iova; /* iova range for updating */
> +		__u64 features; /* virtio features */
> +		__u8 status; /* device status */


Let's add some padding for future extensions.


> +	};
> +};
> +
> +struct vduse_dev_response {
> +	__u32 unique; /* corresponding request id */


Let's use request id.


> +	__s32 result; /* the result of request */


Let's use macro or enum to define the success and failure value.


> +	union {
> +		struct vduse_vq_ready vq_ready; /* virtqueue ready status */
> +		struct vduse_vq_state vq_state; /* virtqueue state */
> +		struct vduse_dev_config_data config; /* virtio device config space */
> +		__u64 features; /* virtio features */
> +		__u8 status; /* device status */
> +	};
> +};
> +
> +/* ioctls */
> +
> +struct vduse_dev_config {
> +	__u32 id; /* vduse device id */
> +	__u32 vendor_id; /* virtio vendor id */
> +	__u32 device_id; /* virtio device id */
> +	__u64 bounce_size; /* bounce buffer size for iommu */
> +	__u16 vq_num; /* the number of virtqueues */
> +	__u16 vq_size_max; /* the max size of virtqueue */
> +	__u32 vq_align; /* the allocation alignment of virtqueue's metadata */
> +};
> +
> +struct vduse_iotlb_entry {
> +	__u64 offset; /* the mmap offset on fd */
> +	__u64 start; /* start of the IOVA range */
> +	__u64 last; /* last of the IOVA range */
> +#define VDUSE_ACCESS_RO 0x1
> +#define VDUSE_ACCESS_WO 0x2
> +#define VDUSE_ACCESS_RW 0x3
> +	__u8 perm; /* access permission of this range */
> +};
> +
> +struct vduse_vq_eventfd {
> +	__u32 index; /* virtqueue index */
> +	__u32 fd; /* eventfd */


Any reason for not using int here?


> +};
> +
> +#define VDUSE_BASE	0x81
> +
> +#define VDUSE_CREATE_DEV	_IOW(VDUSE_BASE, 0x01, struct vduse_dev_config)
> +#define VDUSE_DESTROY_DEV	_IO(VDUSE_BASE, 0x02)
> +
> +#define VDUSE_IOTLB_GET_FD	_IOWR(VDUSE_BASE, 0x04, struct vduse_iotlb_entry)
> +#define VDUSE_VQ_SETUP_KICKFD	_IOW(VDUSE_BASE, 0x05, struct vduse_vq_eventfd)
> +#define VDUSE_VQ_SETUP_IRQFD	_IOW(VDUSE_BASE, 0x06, struct vduse_vq_eventfd)


Better with documentation to explain those ioctls.

Thanks


> +
> +#endif /* _UAPI_VDUSE_H_ */