Subject: Re: [PATCH v12 00/13] Introduce VDUSE - vDPA Device in Userspace

From: "Michael S. Tsirkin" <[email-masked]>
Date: Mon, 10 Jan 2022 07:56:49 -0500

On Mon, Aug 30, 2021 at 10:17:24PM +0800, Xie Yongji wrote:
> This series introduces a framework that makes it possible to implement
> software-emulated vDPA devices in userspace. And to make the device
> emulation more secure, the emulated vDPA device's control path is handled
> in the kernel and only the data path is implemented in the userspace.
> 
> Since the emuldated vDPA device's control path is handled in the kernel,
> a message mechnism is introduced to make userspace be aware of the data
> path related changes. Userspace can use read()/write() to receive/reply
> the 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 software IOTLB 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

It's been half a year - any plans to upstream this?
I'm beginning to worry I made a mistake merging this
with the module being unused by major userspace ...

> To make the userspace VDUSE processes such as qemu-storage-daemon able
> to be run by an unprivileged user. We limit the supported device type
> to virtio block device currently. The support for other device types
> can be added after the security issue of corresponding device driver
> is clarified or fixed in the future.
> 
> Future work:
>   - Improve performance
>   - Userspace library (find a way to reuse device emulation code in qemu/rust-vmm)
>   - Support more device types
> 
> V11 to V12:
> - Rebased to vhost.git
> - Add reset support for all vdpa drivers
> - Remove the dependency on other patches
> - Export eventfd_wake_count
> - Use workqueue for virtqueue kicking in some cases
> 
> V10 to V11:
> - Rebased to newest kernel tree
> - Add a device attribute for message timeout
> - Add check for the reserved field of some structures
> - Add a reset callback in vdpa_config_ops and handle it in VDUSE case
> - Remove the patches that handle virtio-vdpa reset failure
> - Document the structures in include/uapi/linux/vduse.h using kernel doc
> - Add the reserved field for struct vduse_vq_config
> 
> V9 to V10:
> - Forbid some userspace operations after a timeout
> - Rename VDUSE_DEV_INJECT_IRQ to VDUSE_DEV_INJECT_CONFIG_IRQ
> - Use fixed bounce buffer size
> - Fix more code indentation issues in include/linux/vdpa.h
> - Remove the section describing bounce-buffer mechanism in documentation
> - Fix some commit logs and documentation
> 
> V8 to V9:
> - Add VDUSE_SET_STATUS message to replace VDUSE_START/STOP_DATAPLANE messages
> - Support packed virtqueue state
> - Handle the reset failure in both virtio-vdpa and vhost-vdpa cases
> - Add more details in documentation
> - Remove VDUSE_REQ_FLAGS_NO_REPLY flag
> - Add VDUSE_VQ_SETUP ioctl to support per-vq configuration
> - Separate config interrupt injecting out of config update
> - Flush kworker for interrupt inject during resetting
> - Validate the config_size in .get_config()
> 
> V7 to V8:
> - Rebased to newest kernel tree
> - Rework VDUSE driver to handle the device's control path in kernel
> - Limit the supported device type to virtio block device
> - Export free_iova_fast()
> - Remove the virtio-blk and virtio-scsi patches (will send them alone)
> - Remove all module parameters
> - Use the same MAJOR for both control device and VDUSE devices
> - Avoid eventfd cleanup in vduse_dev_release()
> 
> V6 to V7:
> - Export alloc_iova_fast()
> - Add get_config_size() callback
> - Add some patches to avoid trusting virtio devices
> - Add limited device emulation
> - Add some documents
> - Use workqueue to inject config irq
> - Add parameter on vq irq injecting
> - Rename vduse_domain_get_mapping_page() to vduse_domain_get_coherent_page()
> - Add WARN_ON() to catch message failure
> - Add some padding/reserved fields to uAPI structure
> - Fix some bugs
> - Rebase to vhost.git
> 
> V5 to V6:
> - Export receive_fd() instead of __receive_fd()
> - Factor out the unmapping logic of pa and va separatedly
> - Remove the logic of bounce page allocation in page fault handler
> - Use PAGE_SIZE as IOVA allocation granule
> - Add EPOLLOUT support
> - Enable setting API version in userspace
> - Fix some bugs
> 
> V4 to V5:
> - Remove the patch for irq binding
> - Use a single IOTLB for all types of mapping
> - Factor out vhost_vdpa_pa_map()
> - Add some sample codes in document
> - Use receice_fd_user() to pass file descriptor
> - Fix some bugs
> 
> 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 (13):
>   iova: Export alloc_iova_fast() and free_iova_fast()
>   eventfd: Export eventfd_wake_count to modules
>   file: Export receive_fd() to modules
>   vdpa: Fix some coding style issues
>   vdpa: Add reset callback in vdpa_config_ops
>   vhost-vdpa: Handle the failure of vdpa_reset()
>   vhost-iotlb: Add an opaque pointer for vhost IOTLB
>   vdpa: Add an opaque pointer for vdpa_config_ops.dma_map()
>   vdpa: factor out vhost_vdpa_pa_map() and vhost_vdpa_pa_unmap()
>   vdpa: Support transferring virtual addressing during DMA mapping
>   vduse: Implement an MMU-based software IOTLB
>   vduse: Introduce VDUSE - vDPA Device in Userspace
>   Documentation: Add documentation for VDUSE
> 
>  Documentation/userspace-api/index.rst              |    1 +
>  Documentation/userspace-api/ioctl/ioctl-number.rst |    1 +
>  Documentation/userspace-api/vduse.rst              |  233 +++
>  drivers/iommu/iova.c                               |    2 +
>  drivers/vdpa/Kconfig                               |   10 +
>  drivers/vdpa/Makefile                              |    1 +
>  drivers/vdpa/ifcvf/ifcvf_main.c                    |   37 +-
>  drivers/vdpa/mlx5/net/mlx5_vnet.c                  |   42 +-
>  drivers/vdpa/vdpa.c                                |    9 +-
>  drivers/vdpa/vdpa_sim/vdpa_sim.c                   |   26 +-
>  drivers/vdpa/vdpa_user/Makefile                    |    5 +
>  drivers/vdpa/vdpa_user/iova_domain.c               |  545 +++++++
>  drivers/vdpa/vdpa_user/iova_domain.h               |   73 +
>  drivers/vdpa/vdpa_user/vduse_dev.c                 | 1641 ++++++++++++++++++++
>  drivers/vdpa/virtio_pci/vp_vdpa.c                  |   17 +-
>  drivers/vhost/iotlb.c                              |   20 +-
>  drivers/vhost/vdpa.c                               |  168 +-
>  fs/eventfd.c                                       |    1 +
>  fs/file.c                                          |    6 +
>  include/linux/file.h                               |    7 +-
>  include/linux/vdpa.h                               |   62 +-
>  include/linux/vhost_iotlb.h                        |    3 +
>  include/uapi/linux/vduse.h                         |  306 ++++
>  23 files changed, 3112 insertions(+), 104 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
> 
> -- 
> 2.11.0