Re: [Qemu-devel] [PATCH v2 0/6] Start a contrib/libvhost-user

[Michael S. Tsirkin]

On Tue, Oct 18, 2016 at 12:23:59PM +0300, Marc-André Lureau wrote:
> Hi
> 
> vhost-user & virtio have tricky corners and evolve regularly. There
> isn't a reference code that would help you get started either. And the
> backends duplicate most of the effort.

I had to drop this as it got nacked for this release by Stefan.
Sorry about that.
Pls ping or repost after the release.

> Furthermore, due to usage of ancillary data, shared memory, eventfd,
> atomics, it is not so simple to implement in other languages than C
> either. Having a library doing the low-level parts could eventually
> help to reach other languages (this guided some decisions, such as
> being able to override message handling)
> 
> I found it would help me to experiment with new usages of
> libvhost-user (with other devices than network for example) if qemu
> would provide such "reference" library. vhost-user-bridge was the most
> complete attempt at implementing vhost-user slave in qemu, but it
> lacked some abstraction and efficient handling of the virt queues.
> 
> I propose to provide such library based on virtio.c implementation and
> vhost-user-bridge socket handling. It is not meant to be complete, or
> solve all use cases (best efficiency, or multi-threading support are
> not a goal for this first implementation). My hope is that at some
> point the library would be complete and stable enough that it could
> become a standalone project, that could cover most use cases. For now
> it makes more sense to propose it in qemu/contrib as an internal
> library where API could evolve.
> 
> Comments welcome!
> 
> v2:
> - add documentation
> - updated to follow latest virtio queue qemu implementation
> - rename add_watch() to set_watch()
> - various fixes from Felipe Franciosi
> 
> rfc->v1:
> - add vu_gpa_to_va()
> - fix indirect descriptors handling
> - fix notification
> - more error handling
> - disable debugging
> 
> Marc-André Lureau (6):
>   tests/vhost-user-bridge: remove false comment
>   tests/vhost-user-bridge: remove unnecessary dispatcher_remove
>   tests/vhost-user-bridge: indicate peer disconnected
>   tests/vhost-user-bridge: do not accept more than one connection
>   contrib: add libvhost-user
>   tests/vhost-user-bridge: use contrib/libvhost-user
> 
>  contrib/libvhost-user/libvhost-user.c | 1499 
> +++++++++++++++++++++++++++++++++
>  tests/vhost-user-bridge.c             | 1183 +++++---------------------
>  Makefile                              |    1 +
>  Makefile.objs                         |    2 +-
>  contrib/libvhost-user/Makefile.objs   |    1 +
>  tests/Makefile.include                |    2 +-
>  contrib/libvhost-user/libvhost-user.h |  435 ++++++++++
>  7 files changed, 2167 insertions(+), 956 deletions(-)
>  create mode 100644 contrib/libvhost-user/libvhost-user.c
>  create mode 100644 contrib/libvhost-user/Makefile.objs
>  create mode 100644 contrib/libvhost-user/libvhost-user.h
> 
> -- 
> 2.10.0