On Thu, Jan 09, 2014 at 03:59:54PM +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.
>
> We change -mem-path to QemuOpts and add prealloc, share and unlink as
> properties
> to it. HugeTLBFS requirements of -mem-path are relaxed, so any valid path can
> be used now. The new properties allow more fine grained control over the guest
> RAM backing store.
>
> 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.
>
> Example usage:
>
> qemu -m 1024 -mem-path /hugetlbfs,prealloc=on,share=on \
> -netdev type=vhost-user,id=net0,file=/path/to/sock \
Why can't this use standard syntax that qemu_chr_open_socket
supports?
This will add features such as ability for management to open the socket
and pass it to qemu and switch, ability to switch server/client roles,
and others.
> -device virtio-net-pci,netdev=net0
>
> 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)
> - Parse received calls 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 (7):
> Convert -mem-path to QemuOpts and add prealloc,share and unlink
> properties
> Decouple vhost from kernel interface
> Add vhost-user skeleton
> Add domain socket communication for vhost-user backend
> Add vhost-user calls implementation
> Add new vhost-user netdev backend
> Add vhost-user reconnection
>
> exec.c | 57 ++++-
> hmp-commands.hx | 4 +-
> hw/net/vhost_net.c | 144 ++++++++---
> hw/net/virtio-net.c | 42 ++--
> hw/scsi/vhost-scsi.c | 13 +-
> hw/virtio/Makefile.objs | 2 +-
> hw/virtio/vhost-backend.c | 504
> ++++++++++++++++++++++++++++++++++++++
> hw/virtio/vhost.c | 46 ++--
> include/exec/cpu-all.h | 3 -
> include/hw/virtio/vhost-backend.h | 40 +++
> include/hw/virtio/vhost.h | 4 +-
> include/net/vhost-user.h | 17 ++
> include/net/vhost_net.h | 15 +-
> net/Makefile.objs | 2 +-
> net/clients.h | 3 +
> net/hub.c | 1 +
> net/net.c | 2 +
> net/tap.c | 16 +-
> net/vhost-user.c | 167 +++++++++++++
> qapi-schema.json | 18 +-
> qemu-options.hx | 13 +-
> vl.c | 41 +++-
> 22 files changed, 1030 insertions(+), 124 deletions(-)
> create mode 100644 hw/virtio/vhost-backend.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
>
