[RFC,v4,00/11] Introduce VDUSE - vDPA Device in Userspace

Message

Yongji Xie Feb. 23, 2021, 11:50 a.m. UTC

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. 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 type=vduse-blk,id=test,node-name=disk0,writable=on,name=vduse-null,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
  - Userspace library (find a way to reuse device emulation code in qemu/rust-vmm)

V3 to V4:
- Rebase to vhost.git
- Split some patches
- Add some documents
- Use ioctl to inject interrupt rather than eventfd
- Enable config interrupt support
- Support binding irq to the specified cpu
- Add two module parameter to limit bounce/iova size
- Create char device rather than anon inode per vduse
- Reuse vhost IOTLB for iova domain
- Rework the message mechnism in control path

V2 to V3:
- Rework the MMU-based IOMMU driver
- Use the iova domain as iova allocator instead of genpool
- Support transferring vma->vm_file in vhost-vdpa
- Add SVA support in vhost-vdpa
- Remove the patches on bounce pages reclaim

V1 to V2:
- Add vhost-vdpa support
- 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 (11):
  eventfd: Increase the recursion depth of eventfd_signal()
  vhost-vdpa: protect concurrent access to vhost device iotlb
  vhost-iotlb: Add an opaque pointer for vhost IOTLB
  vdpa: Add an opaque pointer for vdpa_config_ops.dma_map()
  vdpa: Support transferring virtual addressing during DMA mapping
  vduse: Implement an MMU-based IOMMU driver
  vduse: Introduce VDUSE - vDPA Device in Userspace
  vduse: Add config interrupt support
  Documentation: Add documentation for VDUSE
  vduse: Introduce a workqueue for irq injection
  vduse: Support binding irq to the specified cpu

 Documentation/userspace-api/index.rst              |    1 +
 Documentation/userspace-api/ioctl/ioctl-number.rst |    1 +
 Documentation/userspace-api/vduse.rst              |  112 ++
 drivers/vdpa/Kconfig                               |   10 +
 drivers/vdpa/Makefile                              |    1 +
 drivers/vdpa/ifcvf/ifcvf_main.c                    |    2 +-
 drivers/vdpa/mlx5/net/mlx5_vnet.c                  |    2 +-
 drivers/vdpa/vdpa.c                                |    9 +-
 drivers/vdpa/vdpa_sim/vdpa_sim.c                   |    8 +-
 drivers/vdpa/vdpa_user/Makefile                    |    5 +
 drivers/vdpa/vdpa_user/iova_domain.c               |  486 +++++++
 drivers/vdpa/vdpa_user/iova_domain.h               |   61 +
 drivers/vdpa/vdpa_user/vduse_dev.c                 | 1399 ++++++++++++++++++++
 drivers/vhost/iotlb.c                              |   20 +-
 drivers/vhost/vdpa.c                               |  106 +-
 fs/eventfd.c                                       |    2 +-
 include/linux/eventfd.h                            |    5 +-
 include/linux/vdpa.h                               |   22 +-
 include/linux/vhost_iotlb.h                        |    3 +
 include/uapi/linux/vduse.h                         |  144 ++
 20 files changed, 2363 insertions(+), 36 deletions(-)
 create mode 100644 Documentation/userspace-api/vduse.rst
 create mode 100644 drivers/vdpa/vdpa_user/Makefile
 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_dev.c
 create mode 100644 include/uapi/linux/vduse.h