Re: [Xen-devel] [RFC PATCH 04/16] x86/xen: hypercall support for xenhost_t

[Andrew Cooper]

On 09/05/2019 18:25, Ankur Arora wrote:
> Allow for different hypercall implementations for different xenhost types.
> Nested xenhost, which has two underlying xenhosts, can use both
> simultaneously.
>
> The hypercall macros (HYPERVISOR_*) implicitly use the default xenhost.x
> A new macro (hypervisor_*) takes xenhost_t * as a parameter and does the
> right thing.
>
> TODO:
>   - Multicalls for now assume the default xenhost
>   - xen_hypercall_* symbols are only generated for the default xenhost.
>
> Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>

Again, what is the hypervisor nesting and/or guest layout here?

I can't think of any case where a single piece of software can
legitimately have two hypercall pages, because if it has one working
one, it is by definition a guest, and therefore not privileged enough to
use the outer one.

~Andrew