Re: [Qemu-devel] [PATCH v1 0/4] Add feature to start QEMU without vhost-user backend

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jun 15, 2015 at 03:12:28PM +0100, Stefan Hajnoczi wrote:
> On Thu, Jun 11, 2015 at 10:56:06AM +0900, Tetsuya Mukawa wrote:
> > On 2015/05/29 13:42, Tetsuya Mukawa wrote:
> > > Hi guys,
> > >
> > > Here are patches to add feature to start QEMU without vhost-user backend.
> > > Currently, if we want to use vhost-user backend, the backend must start before
> > > QEMU. Also, if QEMU or the backend is closed unexpectedly, there is no way to
> > > recover without restarting both applications. Practically, it's not useful.
> > >
> > > This patch series adds following features.
> > >  - QEMU can start before the backend.
> > >  - QEMU or the backend can restart anytime.
> > >    connectivity will be recovered automatically, when app starts again.
> > >    (if QEMU is server, QEMU just wait reconnection)
> > >    while lost connection, link status of virtio-net device is down,
> > >    so virtio-net driver on the guest can know it
> > >
> > > To work like above, the patch introduces flags to specify features vhost-user
> > > backend will support.
> > >
> > > Here are examples.
> > > ('backend_mrg_rxbuf' is an one of new flags. To know all, check the last patch)
> > >
> > >     * QEMU is configured as vhost-user client.
> > >      -chardev socket,id=chr0,path=/tmp/sock,reconnect=3 \
> > >      -netdev vhost-user,id=net0,chardev=chr0,vhostforce,backend_mrg_rxbuf \
> > >      -device virtio-net-pci,netdev=net0 \
> > >
> > >     * QEMU is configured as vhost-user server.
> > >      -chardev socket,id=chr0,path=/tmp/sock,server,nowait \
> > >      -netdev vhost-user,id=net0,chardev=chr0,vhostforce,backend_mrg_rxbuf \
> > >      -device virtio-net-pci,netdev=net0 \
> > >
> > > When virtio-net device is configured by virtio-net driver, QEMU should know
> > > vhost-user backend features. But if QEMU starts without the backend, QEMU cannot
> > > know it. So above the feature values specified by user will be used as features
> > > the backend will support.
> > >
> > > When connection between QEMU and the backend is established, QEMU checkes feature
> > > values of the backend to make sure the expected features are provided.
> > > If it doesn't, the connection will be closed by QEMU.
> > >
> > > Regards,
> > > Tetsuya
> > >
> > > ----------
> > > Changes
> > > ----------
> > > - Changes from RFC patch
> > >   The last patch of this series was changed like below.
> > >    - Rebase to latest master.
> > >    - Remove needless has_backend_feature variable.
> > >    - Change user interface to be able to specify each feature by name.
> > >    - Add (Since 2.4) to schema file.
> > >    - Fix commit title and body.
> > >
> > >
> > > Tetsuya Mukawa (4):
> > >   vhost-user: Add ability to know vhost-user backend disconnection
> > >   vhost-user: Shutdown vhost-user connection when wrong messages are
> > >     passed
> > >   vhost-user: Enable 'nowait' and 'reconnect' option
> > >   vhost-user: Add new option to specify vhost-user backend features
> > >
> > >  hw/net/vhost_net.c             |   6 ++-
> > >  hw/net/virtio-net.c            |  13 +++++
> > >  hw/scsi/vhost-scsi.c           |   2 +-
> > >  hw/virtio/vhost-user.c         |  24 ++++++---
> > >  hw/virtio/vhost.c              |   7 ++-
> > >  include/hw/virtio/vhost.h      |   3 +-
> > >  include/hw/virtio/virtio-net.h |   1 +
> > >  include/net/net.h              |   3 ++
> > >  include/net/vhost_net.h        |   1 +
> > >  include/sysemu/char.h          |   7 +++
> > >  net/net.c                      |   9 ++++
> > >  net/tap.c                      |   1 +
> > >  net/vhost-user.c               |  69 ++++++++++++++++++++++++-
> > >  qapi-schema.json               | 114 +++++++++++++++++++++++++++++++++++------
> > >  qemu-char.c                    |  15 ++++++
> > >  qemu-options.hx                |  10 ++++
> > >  16 files changed, 256 insertions(+), 29 deletions(-)
> > >
> > 
> > Ping.
> > 
> > Could someone please review this patches?
> > http://patchwork.ozlabs.org/project/qemu-devel/list/?submitter=66139
> 
> Nikolay, Jason, or Michael:
> Can one of you please step up to become maintainer of net/vhost-user.c.
> 
> I don't follow vhost-user development much and can't give good review
> feedback about the vhost-user specific aspects.
> 
> Please send a patch that adds you to the MAINTAINERS file for
> net/vhost-user.c.  Then either include merged patches in Michael's pull
> requests or ask me (and in the future, Jason) to include them in net
> pull requests.
> 
> Stefan

Done.