Re: [Xen-devel] Notes on stubdoms and latency on ARM

[Volodymyr Babchuk <vlad.babchuk@xxxxxxxxx>]

Hi Dario,

>> > > On other hand, EL0 app (as I see them) does not need such events.
>> > > Basically, you just call function `handle_mmio()` right in the
>> > > app.
>> > > So, apps can live without interrupts and they still be able to
>> > > handle
>> > > request.
>> >
>> > That's true.
>>
>> Well if they're in a separate security zone, that's not going to
>> work.
>> You have to have a defined interface between things and sanitize
>> inputs
>> between them.
>>
> Exactly, I was about to ask almost the same thing.
>
> In fact, if you are "not" in Xen, as in, you are (and want to be there
> by design) in an entity that is scheduled by Xen, and runs at a
> different privilege level than Xen code, how come you can just call
> random hypervisor functions?
It is impossible, indeed. As I said earlier, interface between app and
hypervisor would be similar to hypercall interface (or it would be
hypercall interface itself).
ARM provides native interface for syscalls in hypervisor mode. That
means, that if you wish, you can handle both hypercalls (as a
hypervisor) and syscalls (as an "OS" for apps).

-- 
WBR Volodymyr Babchuk aka lorc [+380976646013]
mailto: vlad.babchuk@xxxxxxxxx

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