> > > Mojo IPC. Mojo is just yet another IPC designed to work over a Unix > > > socket, relying on file descriptor passing (SCM_RIGHTS) for passing > > > various platform handles (e.g. DMA-bufs). The clients exchange > > > DMA-bufs with the service. > > > > Only dma-bufs? > > > > Mojo is just a framework that can serialize things and pass various > objects around. What is being passed depends on the particular > interface. > > For the camera use case that would be DMA-bufs and fences. Hmm, fences. That'll be tricky too. > We also have some more general use cases where we actually pass files, > sockets and other objects there. They can be easily handled with a > userspace proxy, though. Not very efficiently, but that's not a > requirement for our use cases. Ok. So you'll have a userspace proxy anyway? That pretty much removes the requirement to handle dma-bufs in virtio-vsock (even though that still might be the best option), the proxy could also use virtio-gpu or something else. > > Any ideas or plans for files? > > This is a very interesting problem and also depends on the direction > of transfer. > > Host -> guest should be relatively easy, as reads/writes could go > inline, while guest side mmap could rely on the shared memory to map > the host file mapping into the guest, although I'm not sure how that > would play with the host fs/block subsystems, read aheads, write backs > and so on... > > Guest -> host would be more complicated. In the simplest approach one > could just push the data inline and expose the files locally via FUSE. > Not sure if any memory sharing can be reasonably implemented here, due > to guest side fs/block not aware of the host accessing its memory... One option could be to build on virtio-fs. For files stored elsewhere fallback to inline read/write and maybe simply disallow mmap. cheers, Gerd
