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Re: [Xen-devel] [PATCH v3] xen/arm: introduce PLATFORM_QUIRK_GUEST_PIRQ_NEED_EOI

On Wed, 9 Jul 2014, Julien Grall wrote:
> On 07/09/2014 03:40 PM, Ian Campbell wrote:
> >> I think we should check GIC Dist address passed in DTS by
> >> u-boot to Xen. If GIC Dist address is secured address then
> >> enable the quirk otherwise disable the qurik.
> > 
> > Isn't IGROUPR readable from NS? In which case we should be able to spot
> > the difference, I think?

Anup, can you confirm that we can use IGROUPR to spot the difference?
Otherwise is there another register we can use?

In any case given that only you can test it, I think that it should be
one of you guys that come up with a way to detect the change and submit
a patch to conditionally disable the workaround.

> > Stefano, you might want to arrange in your patch to cache the value of
> > the quirk in the gicv2 struct -- otherwise all the calls to
> > platform_has_quirk are going to add up.
> Can't we cache the value in the platform code? I don't think it's too
> expensive to call the platform_has_quirk in this case.

Caching the value in gic-v2.c seems a bit overkill. But we could turn
platform->quirks() into a bitfield, then we can significantly reduce
memory accesses when checking for quirks, from 3 to just 1.

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