Re: [Xen-devel] Re: Xen's use of PAT and PV guests

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 03/30/2010 10:59 AM, Keir Fraser wrote:
> As it happens I think we do only support CPUs that have PAT. But you can
> always check CPUID, just like running natively.
>    
Yeah, I wasn't going to remove any of the tests, but I was wondering if 
the guest can always assume that it can set the pat flags in the pte.  I 
guess that since Xen uses the same settings for the default pat (=no pat 
at all), then so long as the guest doesn't try to set _PAGE_PAT, then it 
doesn't matter.
Unfortunately hugetlbfs adds a wart, since it appears to end up going 
down to the make_pte/pte_val path, but we can't tell whether its a page 
with _PAGE_PSE or _PAGE_PAT set...
    J

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