Re: Hermetic virtio-vsock in QEMU

[Stefano Garzarella]

Hi,
sorry for the delay, but I have been away most of last month.

On Thu, Apr 18, 2024 at 10:34:43AM GMT, Daniel P. Berrangé wrote:
> On Wed, Apr 17, 2024 at 12:31:41PM -0700, Roman Kiryanov wrote:
> > Hi Daniel,
> >
> > thank you for looking into this. I checked how VHOST_USER_VSOCK and it
> > refers to the vhost-user protocol. It is implemented in the
> > subprojects/libvhost-user library, but this library depends on poll.h
> > and linux/vhost.h files. Do you know if it builds/works on Windows?
>
> Stefano recently ported it to work on any POSIX platform,
> but obviously that still excludes Windows:
>
>  https://lists.nongnu.org/archive/html/qemu-devel/2024-04/msg00388.html
>
> I'm unclear what blockers there are wrt Windows, but perhaps
> Stefano (CC'd) can advise.

I have no experience with Windows, but what we need for vhost-user is:

- AF_UNIX and be able to send file descriptors using ancillary data
  (i.e. SCM_RIGHTS)
- share memory via an fd associated with it (i.e. shm_open(),
  memfd_create(), etc.)
- eventfd or pipe/pipe2 to exchange events (irq and kick)

> Personally, while I think vhost-user is a good option for the
> vast majority of cases, I believe QEMU ought to natively
> implement a simple self contained AF_UNIX backend for vsock,
> avoiding need to depend on 3rd party software for its use.

I was already planning to extrapolate the code that handles this from
vhost-user-vsock to implement a library, this might be a good reason.
Next GSoC?

Thanks,
Stefano