Re: Introduction of stable interface between Xenstore and hypervisor

[Julien Grall <julien@xxxxxxx>]

On 10/09/2021 14:46, Juergen Gross wrote:
> On 10.09.21 15:22, Jan Beulich wrote:
> > On 09.09.2021 08:27, Juergen Gross wrote:
> > > - Addition of a new stable hypercall ("get domain state") returning the
> > >     following information:
> > >     + domid of a domain having the bit set in above bitmap
> > >     + state of that domain (existing, dying)
> > >     + sequence count of that domain
> > >     The related bit is reset in the bitmap as a side effect of the call.
> > What I'd like us to consider up front is whether xenstored is going
> > to remain only entity interested in this kind of information. The
> > entire design looks to leverage that there's only a single consumer
> > in the system.
> Right. I'm just writing some RFC patches, and I have coded this
> interface to be usable only for the domain having VIRQ_DOM_EXC
> registered.
>
> The alternative (IMO) would have been to expose the domain-state
> bitmap to Xenstore (and/or other interested parties).
If we do that, let's do in such way that guest_*_bit() helpers are not 
necessary because they are a massive hammer on Arm. This means the 
bitmap would have to be read-only for the domain.
Cheers,

--
Julien Grall