Re: [virtio-dev] [RFC] Upstreaming virtio-wayland (or an alternative)

[Boris Brezillon <boris.brezillon@collabora.com>]

On Thu, 27 Feb 2020 11:29:17 +0100
Gerd Hoffmann <kraxel@redhat.com> wrote:

> > I'm still unsure how FDs coming from a host application can be
> > converted to resource objects (and then UUIDs so they can be passed
> > to the ipc_connection) if they've not been previously created/passed
> > by the guest though.  
> 
> Depends on the kind of fd I think.  For unix sockets or virtio-fs files
> it should be easy.  dma-bufs or sysv shmem would be more tricky because
> we have to map them into the guest address space (if we want support
> that).  Not impossible though, we could use the new shared memory
> support for that.

I was more worried about the complexity an import_resource() API would
put on the host proxy: it will have to know which subsystem each of the
resources/FDs it tries to pass to the virtio-ipc socket should be
attached to, and none of those resources have actually been created by
the proxy itself. That implies having a way to get that information from
a FD (is it a dmabuf FD, a unix socket fd, ... and depending on the kind
of FD, which device/subsystem is in charge of this FD, for instance, for
dmabufs, you might need to know who allocated the buffer).