Re: Hermetic virtio-vsock in QEMU

[Roman Kiryanov]

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?

I checked how poll.h is used and the only reference I found is "VU_WATCH_IN = POLLIN", no other VU_WATCH_* items seem to be used (the same applies to G_IO_* in -glib.c). Maybe retire VU_WATCH_ and poll.h dependency?

For linux/vhost.h, I see it is gated by defined(__linux__) in libvhost-user.c but not in libvhost-user.h and I think it is not used in libvhost-user.

Regards,

Roman.

On Mon, Apr 15, 2024 at 4:20 AM Daniel P. Berrangé <berrange@redhat.com> wrote:

On Wed, Apr 03, 2024 at 02:30:33PM -0700, Roman Kiryanov wrote:
> Hi Peter, Alex and QEMU,
>
> I work in Android Studio Emulator and we use virtio-vsock to emulate
> devices (e.g. sensors) which live in the Emulator binary. We need to run on
> Windows and in environments without CONFIG_VHOST_VSOCK, that is why we
> cannot use vhost-vsock and invented our implementation. I tried to grep the
> QEMU8 sources and I believe virtio-vsock is not available there.
>
> Do you think it is a good idea to implement virtio-vsock in QEMU (e.g. to
> run on Windows)? If the answer is yes, could you please point where I could
> start to build an upstreamable solution (not Android Emulator specific)? It
> is not clear to me how we should make the device available for clients
> (sensors, modem, adb, etc) in a generic way.

This issue is proposing the idea of exposing VSOCK using AF_UNIX as the
host backend, in a manner that's compatible with that used by firecracker
and cloud-hypervisor:

  https://gitlab.com/qemu-project/qemu/-/issues/2095

Recent versions of Windows support AF_UNIX these days, so hopefully that
would be satisfactory as an approach ?

With regards,
Daniel
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