Re: [Qemu-devel] [PATCH v7 00/13] Vhost and vhost-net support for userspace based backends

[Antonios Motakis]

Hello,


On Mon, Feb 10, 2014 at 9:57 AM, Michael S. Tsirkin <address@hidden> wrote:
>
> On Fri, Jan 31, 2014 at 06:34:29PM +0100, Antonios Motakis wrote:
> > In this patch series we would like to introduce our approach for putting a
> > virtio-net backend in an external userspace process. Our eventual target is 
> > to
> > run the network backend in the Snabbswitch ethernet switch, while receiving
> > traffic from a guest inside QEMU/KVM which runs an unmodified virtio-net
> > implementation.
> >
> > For this, we are working into extending vhost to allow equivalent 
> > functionality
> > for userspace. Vhost already passes control of the data plane of virtio-net 
> > to
> > the host kernel; we want to realize a similar model, but for userspace.
> >
> > In this patch series the concept of a vhost-backend is introduced.
> >
> > We define two vhost backend types - vhost-kernel and vhost-user. The former 
> > is
> > the interface to the current kernel module implementation. Its control 
> > plane is
> > ioctl based. The data plane is the kernel directly accessing the QEMU 
> > allocated,
> > guest memory.
> >
> > In the new vhost-user backend, the control plane is based on communication
> > between QEMU and another userspace process using a unix domain socket. This
> > allows to implement a virtio backend for a guest running in QEMU, inside the
> > other userspace process. For this communication we use a chardev with a 
> > unix socket
> > backend. Vhost-user is client/server agnostic regarding the chardev, however
> > it does not support the 'nowait' and 'telnet' options.
> >
> > We change -mem-path to QemuOpts and add prealloc and share as properties
> > to it. HugeTLBFS is required for this option to work.
> >
> > The data path is realized by directly accessing the vrings and the buffer 
> > data
> > off the guest's memory.
> >
> > The current user of vhost-user is only vhost-net. We add new netdev backend
> > that is intended to initialize vhost-net with vhost-user backend.
>
>
> You mentioned that there will be an in-tree utility that can
> communicate over this channel from the other side.
> Did I miss it in this patchset or is it not included yet?

You haven't missed it; we just wanted to push our intermediate changes
for review, while we were still implementing the in-tree test. The
next version (v8), which we will post quite soon, will include it.


>
>
> > Example usage:
> >
> > qemu -m 1024 -mem-path /hugetlbfs,share=on \
> >      -chardev socket,id=chr0,path=/path/to/socket \
> >      -netdev type=vhost-user,id=net0,chardev=chr0 \
> >      -device virtio-net-pci,netdev=net0
> >
> > This code can be pulled from address@hidden:virtualopensystems/qemu.git 
> > vhost-user-v7
> >
> > A reference vhost-user slave for testing is available from 
> > address@hidden:virtualopensystems/vapp.git
> >
> > TODOs include:
> >  - Include a test in QEMU to avoid regressions
> >  - Slave reconnection and nowait support
> >
> > Changes from v6:
> >  - Remove the 'unlink' property of '-mem-path'
> >  - Extend qemu-char: blocking read, send fds, monitor for connection close
> >  - Vhost-user uses chardev as a backend
> >  - Poll and reconnect removed (no VHOST_USER_ECHO).
> >  - Disconnect is deteced by the chardev (G_IO_HUP event)
> >  - vhost-backend.c split to vhost-user.c
> >
> > Changes from v5:
> >  - Split -mem-path unlink option to a separate patch
> >  - Fds are passed only in the ancillary data
> >  - Stricter message size checks on receive/send
> >  - Netdev vhost-user now includes path and poll_time options
> >  - The connection probing interval is configurable
> >
> > Changes from v4:
> >  - Use error_report for errors
> >  - VhostUserMsg has new field `size` indicating the following payload 
> > length.
> >    Field `flags` now has version and reply bits. The structure is packed.
> >  - Send data is of variable length (`size` field in message)
> >  - Receive in 2 steps, header and payload
> >  - Add new message type VHOST_USER_ECHO, to check connection status
> >
> > Changes from v3:
> >  - Convert -mem-path to QemuOpts with prealloc, share and unlink properties
> >  - Set 1 sec timeout when read/write to the unix domain socket
> >  - Fix file descriptor leak
> >
> > Changes from v2:
> >  - Reconnect when the backend disappears
> >
> > Changes from v1:
> >  - Implementation of vhost-user netdev backend
> >  - Code improvements
> >
> > Antonios Motakis (13):
> >   Convert -mem-path to QemuOpts and add prealloc and share properties
> >   Add chardev API  qemu_chr_fe_read_all
> >   Add chardev API qemu_chr_fe_set_msgfds
> >   Add G_IO_HUP handler for socket chardev
> >   vhost_net should call the poll callback only when it is set
> >   Refactor virtio-net to use a generic get_vhost_net
> >   vhost_net_init will use VhostNetOptions to get all its arguments
> >   Add vhost_ops to the vhost_dev struct and replace all relevant ioctls
> >   Add vhost-backend and VhostBackendType
> >   Add vhost-user as a vhost backend.
> >   Add new vhost-user netdev backend
> >   Add the vhost-user netdev backend to command line
> >   Add vhost-user protocol documentation
> >
> >  docs/specs/vhost-user.txt         | 249 ++++++++++++++++++++++++++++
> >  exec.c                            |  30 +++-
> >  hmp-commands.hx                   |   4 +-
> >  hw/net/vhost_net.c                | 142 +++++++++++-----
> >  hw/net/virtio-net.c               |  42 ++---
> >  hw/scsi/vhost-scsi.c              |  20 ++-
> >  hw/virtio/Makefile.objs           |   2 +-
> >  hw/virtio/vhost-backend.c         |  71 ++++++++
> >  hw/virtio/vhost-user.c            | 331 
> > ++++++++++++++++++++++++++++++++++++++
> >  hw/virtio/vhost.c                 |  55 ++++---
> >  include/exec/cpu-all.h            |   3 -
> >  include/hw/virtio/vhost-backend.h |  38 +++++
> >  include/hw/virtio/vhost.h         |   8 +-
> >  include/net/vhost-user.h          |  17 ++
> >  include/net/vhost_net.h           |  11 +-
> >  include/sysemu/char.h             |  28 ++++
> >  net/Makefile.objs                 |   2 +-
> >  net/clients.h                     |   3 +
> >  net/hub.c                         |   1 +
> >  net/net.c                         |   2 +
> >  net/tap.c                         |  18 ++-
> >  net/vhost-user.c                  | 217 +++++++++++++++++++++++++
> >  qapi-schema.json                  |  18 ++-
> >  qemu-char.c                       | 185 ++++++++++++++++++++-
> >  qemu-options.hx                   |  25 ++-
> >  vl.c                              |  37 ++++-
> >  26 files changed, 1425 insertions(+), 134 deletions(-)
> >  create mode 100644 docs/specs/vhost-user.txt
> >  create mode 100644 hw/virtio/vhost-backend.c
> >  create mode 100644 hw/virtio/vhost-user.c
> >  create mode 100644 include/hw/virtio/vhost-backend.h
> >  create mode 100644 include/net/vhost-user.h
> >  create mode 100644 net/vhost-user.c
> >
> > --
> > 1.8.3.2
> >




-- 
Antonios Motakis
Virtual Open Systems