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

[Yongji Xie]

On Mon, Jan 10, 2022 at 8:57 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> 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?

Yeah, this is on my to-do list this month.

Sorry for taking so long... I've been working on another project
enabling userspace RDMA with VDUSE for the past few months. So I
didn't have much time for this. Anyway, I will submit the first
version as soon as possible.

Thanks,
Yongji