Re: [XenPPC] Re: IRQs delivery.

[Olof Johansson <olof@xxxxxxxxx>]

On Fri, Mar 10, 2006 at 09:27:50PM -0500, Jimi Xenidis wrote:
> 
> >Not that you have a choice on PPC970,
> 
> This _is_ the case for 970 as well (it was not the case for POWER4).

Since POWER4 didn't have a hypervisor that allowed shared processors,
I guess this wasn't much of a problem. (Well, maybe seen the other
way the lack of the processor feature kept them from adding shared
processor support).

> >Some PPC processors have a feature called "mediated external  
> >interrupts",
> >where they will be delivered to the hypervisor instead,
> 
> MEI does not make this descision.. the LPES does.

Right. Hollis threw me off by saying that interrupts go to the domain,
leading me to believe the two features were introduced at the same time.
Especially since both MEI and HV/SV delivery are configured via LPES.

> Yes it is for Cell and other forth-comming processors.  It is really  
> for latency issues of RTOS (and games), server workloads are not  
> expected to ever need this.

Yep, you'd definitely want it on a desktop running a hypervisor too.
Classic server workloads are obviously not nearly as latency sensitive.


-Olof

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