Re: [RFC v2 06/13] vduse: Introduce VDUSE - vDPA Device in Userspace

[Yongji Xie <xieyongji@bytedance.com>]

On Wed, Dec 23, 2020 at 4:08 PM Jason Wang <jasowang@redhat.com> wrote:
>
>
> On 2020/12/22 下午10:52, 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, the VDUSE driver implements a MMU-based on-chip
> > IOMMU driver which supports mapping the kernel dma buffer to a
> > userspace iova region dynamically. Userspace can access those
> > iova region via mmap(). Besides, the eventfd mechanism is used to
> > trigger interrupt callbacks and receive virtqueue kicks in userspace
> >
> > Now we only support virtio-vdpa bus driver with this patch applied.
> >
> > Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
> > ---
> >   Documentation/driver-api/vduse.rst                 |   74 ++
> >   Documentation/userspace-api/ioctl/ioctl-number.rst |    1 +
> >   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               |  442 ++++++++
> >   drivers/vdpa/vdpa_user/iova_domain.h               |   93 ++
> >   drivers/vdpa/vdpa_user/vduse.h                     |   59 ++
> >   drivers/vdpa/vdpa_user/vduse_dev.c                 | 1121 ++++++++++++++++++++
> >   include/uapi/linux/vdpa.h                          |    1 +
> >   include/uapi/linux/vduse.h                         |   99 ++
> >   13 files changed, 2173 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..da9b3040f20a
> > --- /dev/null
> > +++ b/Documentation/driver-api/vduse.rst
> > @@ -0,0 +1,74 @@
> > +==================================
> > +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.
> > +Those control messages are 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.
> > +
> > +- 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_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
> > +
> > +Please see include/linux/vdpa.h for details.
> > +
> > +In the data path, VDUSE framework implements a MMU-based on-chip IOMMU
> > +driver which supports mapping the kernel dma buffer to a userspace iova
> > +region dynamically. The userspace iova region can be created by passing
> > +the userspace vDPA device 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
> > +----------------------
> > +The basic idea behind the IOMMU driver is treating MMU (VA->PA) as
> > +IOMMU (IOVA->PA). This 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..211cc449cbd3 100644
> > --- a/drivers/vdpa/Kconfig
> > +++ b/drivers/vdpa/Kconfig
> > @@ -21,6 +21,14 @@ 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
>
>
> The "default n" is not necessary.
>

OK.
>
> > +     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
>
>
> Do we really need eventfd.o here consider we've selected it.
>

Do you mean the file "drivers/vdpa/vdpa_user/eventfd.c"?

>
> > +
> > +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);
>
>
> Any reason that a workqueue is must here?
>

Mainly for performance considerations. Make sure the push() and pop()
for used vring can be asynchronous.

> > +
> > +     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..27022157abc6
> > --- /dev/null
> > +++ b/drivers/vdpa/vdpa_user/iova_domain.c
> > @@ -0,0 +1,442 @@
> > +// 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/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 12
> > +#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 inline struct vduse_iova_map *
> > +vduse_domain_get_iova_map(struct vduse_iova_domain *domain,
> > +                             unsigned long iova)
> > +{
> > +     unsigned long index = iova >> IOVA_CHUNK_SHIFT;
> > +     unsigned long chunkoff = iova & ~IOVA_CHUNK_MASK;
> > +     unsigned long mapindex = chunkoff >> IOVA_ALLOC_ORDER;
> > +
> > +     return domain->chunks[index].iova_map[mapindex];
> > +}
> > +
> > +static inline void
> > +vduse_domain_set_iova_map(struct vduse_iova_domain *domain,
> > +                     unsigned long iova, struct vduse_iova_map *map)
> > +{
> > +     unsigned long index = iova >> IOVA_CHUNK_SHIFT;
> > +     unsigned long chunkoff = iova & ~IOVA_CHUNK_MASK;
> > +     unsigned long mapindex = chunkoff >> IOVA_ALLOC_ORDER;
> > +
> > +     domain->chunks[index].iova_map[mapindex] = map;
> > +}
> > +
> > +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;
> > +     unsigned long last = iova + size;
> > +
> > +     map = kzalloc(sizeof(struct vduse_iova_map), GFP_ATOMIC);
> > +     if (!map)
> > +             return -ENOMEM;
> > +
> > +     map->iova = iova;
> > +     map->orig = orig;
> > +     map->size = size;
> > +     map->dir = dir;
> > +
> > +     while (iova < last) {
> > +             vduse_domain_set_iova_map(domain, iova, map);
> > +             iova += IOVA_ALLOC_SIZE;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +struct vduse_iova_map *
> > +vduse_domain_get_mapping(struct vduse_iova_domain *domain,
> > +                     unsigned long iova)
> > +{
> > +     return vduse_domain_get_iova_map(domain, iova);
> > +}
> > +
> > +void vduse_domain_remove_mapping(struct vduse_iova_domain *domain,
> > +                             struct vduse_iova_map *map)
> > +{
> > +     unsigned long iova = map->iova;
> > +     unsigned long last = iova + map->size;
> > +
> > +     while (iova < last) {
> > +             vduse_domain_set_iova_map(domain, iova, NULL);
> > +             iova += IOVA_ALLOC_SIZE;
> > +     }
> > +}
> > +
> > +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 page *page = NULL;
> > +
> > +     map = vduse_domain_get_iova_map(domain, iova);
> > +     if (map) {
> > +             offset = last - map->iova;
> > +             page = virt_to_page(map->orig + offset);
> > +     }
> > +
> > +     return page ? vm_insert_page(vma, uaddr, page) : -EFAULT;
> > +}
>
>
> So as we discussed before, we need to find way to make vhost work. And
> it's better to make vhost transparent to VDUSE. One idea is to implement
> shadow virtqueue here, that is, instead of trying to insert the pages to
> VDUSE userspace, we use the shadow virtqueue to relay the descriptors to
> userspace. With this, we don't need stuffs like shmfd etc.
>

Good idea! The disadvantage is performance will go down (one more
thread switch overhead and vhost-liked kworker will become bottleneck
without multi-thread support). I think I can try this in v3. And the
MMU-based IOMMU implementation can be a future optimization in the
virtio-vdpa case. What's your opinion?

>
> > +
> > +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);
> > +             }
>
>
> I think I miss something, for DMA_FROM_DEVICE, if p doesn't exist how is
> it expected to work? Or do we need to warn here in this case?
>

Yes, I think we need a WARN_ON here.


>
> > +             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 offset = 0;
> > +     bool found = false;
> > +     struct vduse_iova_map *map;
> > +     struct page *page;
> > +
> > +     mutex_lock(&domain->map_lock);
> > +
> > +     page = vduse_domain_get_bounce_page(domain, iova);
> > +     if (page)
> > +             goto unlock;
> > +
> > +     page = alloc_page(GFP_KERNEL);
> > +     if (!page)
> > +             goto unlock;
> > +
> > +     while (offset < PAGE_SIZE) {
> > +             unsigned int src_offset = 0, dst_offset = 0;
> > +             void *src, *dst;
> > +             size_t copy_len;
> > +
> > +             map = vduse_domain_get_iova_map(domain, start + offset);
> > +             if (!map) {
> > +                     offset += IOVA_ALLOC_SIZE;
> > +                     continue;
> > +             }
> > +
> > +             found = true;
> > +             offset += map->size;
> > +             if (map->dir == DMA_FROM_DEVICE)
> > +                     continue;
> > +
> > +             if (start > map->iova)
> > +                     src_offset = start - map->iova;
> > +             else
> > +                     dst_offset = map->iova - 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);
> > +     }
> > +     if (!found) {
> > +             put_page(page);
> > +             page = NULL;
> > +     }
> > +     vduse_domain_set_bounce_page(domain, iova, page);
> > +unlock:
> > +     mutex_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;
>
>
> I wonder why not just reuse the iova domain implements in
> driver/iommu/iova.c
>

The iova domain in driver/iommu/iova.c is only an iova allocator which
is implemented by the genpool memory allocator in our case. The other
part in our iova domain is chunk management and iova_map management.
We need different chunks to distinguish different dma mapping types:
consistent mapping or streaming mapping. We can only use
bouncing-mechanism in the streaming mapping case.

>
> > +}
> > +
> > +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);
> > +     vfree(chunk->iova_map);
> > +     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->map_lock);
> > +     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->iova_map = vzalloc((size >> IOVA_ALLOC_ORDER) *
> > +                             sizeof(struct vduse_iova_map *));
> > +     if (!chunk->iova_map)
> > +             goto err;
> > +
> > +     chunk->start = addr;
> > +     atomic_set(&chunk->map_type, TYPE_NONE);
> > +
> > +     return 0;
> > +err:
> > +     if (chunk->bounce_pages) {
> > +             vfree(chunk->bounce_pages);
> > +             chunk->bounce_pages = NULL;
> > +     }
> > +     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;
> > +     INIT_LIST_HEAD(&domain->vma_list);
> > +     mutex_init(&domain->vma_lock);
> > +     mutex_init(&domain->map_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..fe1816287f5f
> > --- /dev/null
> > +++ b/drivers/vdpa/vdpa_user/iova_domain.h
> > @@ -0,0 +1,93 @@
> > +/* 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/genalloc.h>
> > +#include <linux/dma-mapping.h>
> > +
> > +enum iova_map_type {
> > +     TYPE_NONE,
> > +     TYPE_DIRECT_MAP,
> > +     TYPE_BOUNCE_MAP,
> > +};
> > +
> > +struct vduse_iova_map {
> > +     unsigned long iova;
> > +     unsigned long orig;
> > +     size_t size;
> > +     enum dma_data_direction dir;
> > +};
> > +
> > +struct vduse_iova_chunk {
> > +     struct gen_pool *pool;
> > +     struct page **bounce_pages;
> > +     struct vduse_iova_map **iova_map;
> > +     unsigned long start;
> > +     atomic_t map_type;
> > +};
> > +
> > +struct vduse_iova_domain {
> > +     struct vduse_iova_chunk *chunks;
> > +     int chunk_num;
> > +     size_t size;
> > +     struct mutex map_lock;
> > +     struct mutex vma_lock;
> > +     struct list_head vma_list;
> > +};
>
>
> It's better to explain why you need to organize the bounce buffer with
> chunks by adding some comments above or in the commit log. Is this
> because you want to have O(1) for finding the page for a specific IOVA?
>

It is used to distinguish different dma mapping type as above said.


>
> > +
> > +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);
> > +
> > +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..1041ce7bddc4
> > --- /dev/null
> > +++ b/drivers/vdpa/vdpa_user/vduse.h
> > @@ -0,0 +1,59 @@
> > +/* 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 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;
> > +     refcount_t refcnt;
> > +     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..4a869b9698ef
> > --- /dev/null
> > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> > @@ -0,0 +1,1121 @@
> > +// 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;
> > +};
> > +
> > +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_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 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);
> > +
> > +     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 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->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 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;
> > +}
> > +
> > +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)
>
>
> How about bidirectional mapping?
>

Will fix it.

>
> > +             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);
> > +
> > +     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);
> > +
> > +     if (WARN_ON(!map))
> > +             return;
> > +
> > +     vduse_domain_remove_mapping(domain, map);
> > +     vduse_domain_unmap(domain, map->iova, PAGE_ALIGN(map->size));
> > +     free_pages_exact((void *)map->orig, map->size);
> > +     vduse_domain_free_iova(domain, map->iova, 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;
> > +     if (ret < 0 && ret != -EBUSY)
> > +             return VM_FAULT_SIGBUS;
> > +
> > +     return VM_FAULT_NOPAGE;
> > +}
> > +
> > +static const struct vm_operations_struct vduse_dev_mmap_ops = {
> > +     .open = vduse_dev_mmap_open,
> > +     .close = vduse_dev_mmap_close,
> > +     .may_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 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_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);
> > +
> > +     refcount_dec(&dev->refcnt);
> > +
> > +     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);
> > +     refcount_set(&dev->refcnt, 1);
> > +
> > +     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;
> > +
> > +     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;
> > +
> > +     refcount_inc(&dev->refcnt);
> > +
> > +     return fd;
> > +}
> > +
> > +static int vduse_destroy_dev(u32 id)
> > +{
> > +     struct vduse_dev *dev = vduse_find_dev(id);
> > +
> > +     if (!dev)
> > +             return -EINVAL;
> > +
> > +     if (dev->vdev || refcount_read(&dev->refcnt) > 1)
> > +             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;
> > +
> > +     refcount_inc(&dev->refcnt);
> > +     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;
>
>
> What's the use case of VDUSE_GET_DEV? (Need to document this)
>

It is used to get the device fd after VDUSE daemon reboot/crash, I
will split this into another patch and document it.

Thanks,
Yongji