Messages in this thread | | | Date | Sun, 01 Mar 2009 15:52:24 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH] xen: core dom0 support |
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Jeremy Fitzhardinge wrote: > > Unless we're planning on dropping support for processes with no or > broken PAT support, we're always going to have to deal with the non-PAT > case. Xen just falls into the "processor with no PAT" case. And > if/when we work out how to paravirtualize PAT, it will no longer be in > that case. >
In this particular case, this is actually false. "No PAT" in the processor is *not* the same thing as "no cacheability controls in the page tables". Every processor since the 386 has had UC, WT, and WB controls in the page tables; PAT only added the ability to do WC (and WP, which we don't use). Since the number of processors which can do WC at all but don't have PAT is a small set of increasingly obsolete processors, we may very well choose to simply ignore the WC capabilities of these particular processors.
-hpa
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