On Fri, Jan 18, 2008 at 10:02:10PM +0100, Ingo Molnar wrote:
>
> * Dave Jones <[EMAIL PROTECTED]> 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?
A crazy idea just occured to me.. We could make /proc/mtrr an interface
to set PAT on a range of memory. This would make it transparently work
without any changes in X or anything else that sets them in userspace.
Dave
--
http://www.codemonkey.org.uk
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