On Mon, Jan 13, 2014 at 03:25:11PM +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.
Wait a second. This does not actually work well: if you mmap a random file outside HugeTLBFS, kernel won't create huge pages from this memory so performance of the system as a whole will suffer. You'll have fix the kernel MM before this scheme can fly. > 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,path=/path/to/sock,poll_time=2500 \ > -device virtio-net-pci,netdev=net0 > > 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 (8): > Convert -mem-path to QemuOpts and add prealloc and share properties > New -mem-path option - unlink. > 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 | 556 > ++++++++++++++++++++++++++++++++++++++ > 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 | 177 ++++++++++++ > qapi-schema.json | 21 +- > qemu-options.hx | 24 +- > vl.c | 41 ++- > 22 files changed, 1106 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 >
