From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: Re: Xen's use of PAT and PV guests
Date: Tue, 30 Mar 2010 11:25:32 -0700
Message-ID: <4BB2421C.3060901@goop.org>
References: <C7D7FA76.F17A%keir.fraser@eu.citrix.com>
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To: Keir Fraser <keir.fraser@eu.citrix.com>
Cc: Xen-devel <xen-devel@lists.xensource.com>, Dave McCracken <dave.mccracken@oracle.com>, Jan Beulich <JBeulich@novell.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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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