Re: Notes on stubdoms and latency on ARM

[Volodymyr Babchuk <vlad.babchuk@gmail.com>]

Hello Juilen,
>> The polling can be minimized if you block the vCPU when there are
>> nothing to do. It would get unblock when you have to schedule him
>> because of a request.
> Thinking a bit more about this. So far, we rely on the domain to use the
> vGIC interrupt controller which require the context switch.
>
> We could also implement a dummy interrupt controller to handle a predefined
> limited amount of interrupts which would allow asynchronous support in
> stubdom and an interface to support upcall via the interrupt exception
> vector.
>
> This is something that would be more tricky to do with EL0 app as there is
> no EL0 vector exception.
>
Actually, your idea about blocking vcpu is very interesting. Then we
don't need vGIC at all. For example, when stubdomain have finished
handling request, it can issue hypercall "block me until new
requests". XEN blocks vcpu at this moment and unblocks it only when
there are another request ready. This is very promising idea. Need to
think about it further.

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

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