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SubjectRe: [PATCH] X86: fix typo PAT to X86_PAT

* Dave Jones <davej@redhat.com> wrote:

> > 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.

there's no exclusion enforced right now, and if a CPU is PAT-incapable
(or if the kernel is booted nopat) then the MTRR bits should be usable.
But if we boot with PAT enabled, and Xorg gets /proc/mtrr wrong, we'll
see nasty crashes. If it gets them right, it should all still work just
fine. Is this ok? Then, in a year or two, distros can disable write
support to /proc/mtrr. Hm?

Ingo


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