Re: [RFC v2 00/13] Introduce VDUSE - vDPA Device in Userspace

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On 2020/12/22 下午10:52, Xie Yongji wrote:
This series introduces a framework, which can be used to implement
vDPA Devices in a userspace program. The work consist of two parts:
control path forwarding and data path offloading.

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 core is mapping dma buffer into VDUSE
daemon's address space, which can be implemented in different ways
depending on the vdpa bus to which the vDPA device is attached.

In virtio-vdpa case, we implements a MMU-based on-chip IOMMU driver with
bounce-buffering mechanism to achieve that.


Rethink about the bounce buffer stuffs. I wonder instead of using kernel pages with mmap(), how about just use userspace pages like what vhost did?

It means we need a worker to do bouncing but we don't need to care about annoying stuffs like page reclaiming?


And in vhost-vdpa case, the dma
buffer is reside in a userspace memory region which can be shared to the
VDUSE userspace processs via transferring the shmfd.

The details and our user case is shown below:

------------------------    -------------------------   ----------------------------------------------
|            Container |    |              QEMU(VM) |   |                               VDUSE daemon |
|       ---------      |    |  -------------------  |   | ------------------------- ---------------- |
|       |dev/vdx|      |    |  |/dev/vhost-vdpa-x|  |   | | vDPA device emulation | | block driver | |
------------+-----------     -----------+------------   -------------+----------------------+---------
             |                           |                            |                      |
             |                           |                            |                      |
------------+---------------------------+----------------------------+----------------------+---------
|    | block device |           |  vhost device |            | vduse driver |          | TCP/IP |    |
|    -------+--------           --------+--------            -------+--------          -----+----    |
|           |                           |                           |                       |        |
| ----------+----------       ----------+-----------         -------+-------                |        |
| | virtio-blk driver |       |  vhost-vdpa driver |         | vdpa device |                |        |
| ----------+----------       ----------+-----------         -------+-------                |        |
|           |      virtio bus           |                           |                       |        |
|   --------+----+-----------           |                           |                       |        |
|                |                      |                           |                       |        |
|      ----------+----------            |                           |                       |        |
|      | virtio-blk device |            |                           |                       |        |
|      ----------+----------            |                           |                       |        |
|                |                      |                           |                       |        |
|     -----------+-----------           |                           |                       |        |
|     |  virtio-vdpa driver |           |                           |                       |        |
|     -----------+-----------           |                           |                       |        |
|                |                      |                           |    vdpa bus           |        |
|     -----------+----------------------+---------------------------+------------           |        |
|                                                                                        ---+---     |
-----------------------------------------------------------------------------------------| NIC |------
                                                                                          ---+---
                                                                                             |
                                                                                    ---------+---------
                                                                                    | Remote Storages |
                                                                                    -------------------

We make use of it to implement a block device connecting to
our distributed storage, which can be used both in containers and
VMs. Thus, we can have an unified technology stack in this two cases.

To test it with null-blk:

   $ qemu-storage-daemon \
       --chardev socket,id=charmonitor,path=/tmp/qmp.sock,server,nowait \
       --monitor chardev=charmonitor \
       --blockdev driver=host_device,cache.direct=on,aio=native,filename=/dev/nullb0,node-name=disk0 \
       --export vduse-blk,id=test,node-name=disk0,writable=on,vduse-id=1,num-queues=16,queue-size=128

The qemu-storage-daemon can be found at https://github.com/bytedance/qemu/tree/vduse

Future work:
   - Improve performance (e.g. zero copy implementation in datapath)
   - Config interrupt support
   - Userspace library (find a way to reuse device emulation code in qemu/rust-vmm)

This is now based on below series:
https://lore.kernel.org/netdev/20201112064005.349268-1-parav@xxxxxxxxxx/

V1 to V2:
- Add vhost-vdpa support


I may miss something but I don't see any code to support that. E.g neither set_map nor dma_map/unmap is implemented in the config ops.

Thanks


- Add some documents
- Based on the vdpa management tool
- Introduce a workqueue for irq injection
- Replace interval tree with array map to store the iova_map

Xie Yongji (13):
   mm: export zap_page_range() for driver use
   eventfd: track eventfd_signal() recursion depth separately in different cases
   eventfd: Increase the recursion depth of eventfd_signal()
   vdpa: Remove the restriction that only supports virtio-net devices
   vdpa: Pass the netlink attributes to ops.dev_add()
   vduse: Introduce VDUSE - vDPA Device in Userspace
   vduse: support get/set virtqueue state
   vdpa: Introduce process_iotlb_msg() in vdpa_config_ops
   vduse: Add support for processing vhost iotlb message
   vduse: grab the module's references until there is no vduse device
   vduse/iova_domain: Support reclaiming bounce pages
   vduse: Add memory shrinker to reclaim bounce pages
   vduse: Introduce a workqueue for irq injection

  Documentation/driver-api/vduse.rst                 |   91 ++
  Documentation/userspace-api/ioctl/ioctl-number.rst |    1 +
  drivers/vdpa/Kconfig                               |    8 +
  drivers/vdpa/Makefile                              |    1 +
  drivers/vdpa/vdpa.c                                |    2 +-
  drivers/vdpa/vdpa_sim/vdpa_sim.c                   |    3 +-
  drivers/vdpa/vdpa_user/Makefile                    |    5 +
  drivers/vdpa/vdpa_user/eventfd.c                   |  229 ++++
  drivers/vdpa/vdpa_user/eventfd.h                   |   48 +
  drivers/vdpa/vdpa_user/iova_domain.c               |  517 ++++++++
  drivers/vdpa/vdpa_user/iova_domain.h               |  103 ++
  drivers/vdpa/vdpa_user/vduse.h                     |   59 +
  drivers/vdpa/vdpa_user/vduse_dev.c                 | 1373 ++++++++++++++++++++
  drivers/vhost/vdpa.c                               |   34 +-
  fs/aio.c                                           |    3 +-
  fs/eventfd.c                                       |   20 +-
  include/linux/eventfd.h                            |    5 +-
  include/linux/vdpa.h                               |   11 +-
  include/uapi/linux/vdpa.h                          |    1 +
  include/uapi/linux/vduse.h                         |  119 ++
  mm/memory.c                                        |    1 +
  21 files changed, 2598 insertions(+), 36 deletions(-)
  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





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