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? > 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 g...@github.com:virtualopensystems/qemu.git > vhost-user-v7 > > A reference vhost-user slave for testing is available from > g...@github.com: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 >