Re: [Xen-devel] [PATCH] libxc: Expose the pdpe1gb cpuid flag to guest

[Tim Deegan <tim@xxxxxxx>]

At 01:29 +0000 on 19 Nov (1416356943), Zhang, Yang Z wrote:
> Tim Deegan wrote on 2014-11-18:
> > In this case, the guest is entitled to _expect_ pagefaults on 1GB
> > mappings if CPUID claims they are not supported.  That sounds like an
> > unlikely thing for the guest to be relying on, but Xen itself does
> > something similar for the SHOPT_FAST_FAULT_PATH (and now also for
> > IOMMU entries for the deferred caching attribute updates).
> 
> Indeed. How about adding the software check (as Andrew mentioned)
> firstly and leave the hardware problem (Actually, I don't think we
> can solve it currently).

I don't think we should change the software path unless we can change
the hardware behaviour too.  It's better to be consistent, and it
saves us some cycles in the pt walker.

Cheers,

Tim.

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