Re: Virtio on Xen with Rust

[Wei Liu <wl@xxxxxxx>]

Hi Viresh

This is very cool.

On Thu, Apr 14, 2022 at 02:53:58PM +0530, Viresh Kumar wrote:
> +xen-devel
> 
> On 14-04-22, 14:45, Viresh Kumar wrote:
> > Hello,
> > 
> > We verified our hypervisor-agnostic Rust based vhost-user backends with Qemu
> > based setup earlier, and there was growing concern if they were truly
> > hypervisor-agnostic.
> > 
> > In order to prove that, we decided to give it a try with Xen, a type-1
> > bare-metal hypervisor.
> > 
> > We are happy to announce that we were able to make progress on that front 
> > and
> > have a working setup where we can test our existing Rust based backends, 
> > like
> > I2C, GPIO, RNG (though only I2C is tested as of now) over Xen.
> > 
> > Key components:
> > --------------
> > 
> > - Xen: https://github.com/vireshk/xen
> > 
> >   Xen requires MMIO and device specific support in order to populate the
> >   required devices at the guest. This tree contains four patches on the top 
> > of
> >   mainline Xen, two from Oleksandr (mmio/disk) and two from me (I2C).
> > 
> > - libxen-sys: https://github.com/vireshk/libxen-sys
> > 
> >   We currently depend on the userspace tools/libraries provided by Xen, like
> >   xendevicemodel, xenevtchn, xenforeignmemory, etc. This crates provides 
> > Rust
> >   wrappers over those calls, generated automatically with help of bindgen
> >   utility in Rust, that allow us to use the installed Xen libraries. Though 
> > we
> >   plan to replace this with Rust based "oxerun" (find below) in longer run.
> > 
> > - oxerun (WIP): https://gitlab.com/mathieupoirier/oxerun/-/tree/xen-ioctls
> > 

> >   This is Rust based implementations for Ioctl and hypercalls to Xen. This 
> > is WIP
> >   and should eventually replace "libxen-sys" crate entirely (which are C 
> > based
> >   implementation of the same).
> > 

I'm curious to learn why there is a need to replace libxen-sys with the
pure Rust implementation. Those libraries (xendevicemodel, xenevtchn,
xenforeignmemory) are very stable and battle tested. Their interfaces
are stable.

Thanks,
Wei.