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SubjectRe: [PATCH] X86: fix typo PAT to X86_PAT
On Fri, Jan 18, 2008 at 01:31:40PM +0100, Ingo Molnar wrote:

> * Yinghai Lu <Yinghai.Lu@Sun.COM> wrote:
> > > thanks. But, i think we should rather do the following: if X86_PAT
> > > is eanbled then /proc/mtrr should be read-only. There's no problem
> > > _looking_ at MTRR contents, as long as we do not try to modify them.
> > > Hm?
> >
> > anyway
> >
> > depends on !PAT
> >
> > need to be removed.
> >
> > it seems when PAT is used, some code still touch MTRR.
> you mean modifies MTRRs? Which code is that? (besides the /proc/mtrr
> userspace API)

This exclusion is going to be a real pain in the ass for distro kernels.
It's impossible for example to build a kernel that will now support
the MTRR-alike registers on the AMD K6/early Cyrix etc and also
support PAT.

Additionally, given people tend to update their kernels a lot more often
than they update to a whole new version of X, it means until userspace
has caught up, we can't ship a kernel with PAT supported, or else
X gets a lot slower due to the missing mtrr support.



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