Re: [PATCH v3 4/4] docs: vhost-user: add subsection for non-Linux platforms

[Michael S. Tsirkin]

On Thu, Mar 03, 2022 at 12:59:11PM +0100, Sergio Lopez wrote:
> Add a section explaining how vhost-user is supported on platforms
> other than Linux.
> 
> Signed-off-by: Sergio Lopez <slp@redhat.com>
> ---
>  docs/interop/vhost-user.rst | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst
> index edc3ad84a3..590a626b92 100644
> --- a/docs/interop/vhost-user.rst
> +++ b/docs/interop/vhost-user.rst
> @@ -38,6 +38,24 @@ conventions <backend_conventions>`.
>  *Master* and *slave* can be either a client (i.e. connecting) or
>  server (listening) in the socket communication.
>  
> +Support for platforms other than Linux


It's not just Linux - any platform without eventfd.

So I think we should have a section explaining that whereever
spec says eventfd it can be a pipe if system does not
support creating eventfd.

> +--------------------------------------
> +
> +While vhost-user was initially developed targeting Linux, nowadays is
> +supported on any platform that provides the following features:
> +
> +- The ability to share a mapping injected into the guest between
> +  multiple processes, so both QEMU and the vhost-user daemon servicing
> +  the device can access simultaneously the memory regions containing
> +  the virtqueues and the data associated with each request.
> +
> +- AF_UNIX sockets with SCM_RIGHTS, so QEMU can communicate with the
> +  vhost-user daemon and send it file descriptors when needed.
> +
> +- Either eventfd or pipe/pipe2. On platforms where eventfd is not
> +  available, QEMU will automatically fallback to pipe2 or, as a last
> +  resort, pipe.
> +
>  Message Specification
>  =====================
>  
> -- 
> 2.35.1