Re: [PATCH]: Fix MTRR handling on HT CPUs (improved)

[Linus Torvalds]

On Fri, 25 Jan 2002, Alan Cox wrote:
>
> > I strongly suspected somebody else must have hit this problem before, but
> > intensive research did show up nothing. Also my first post on LK
> > received no "hey, that's old stuff" answer. So here I go.
>
> A tiny patch was posted about 4-6 months ago
>
> The patch is total overkill. Just remove the error reporting if the right
> firmware was already loaded. You've written a fixup wrapper around a
> rather nonsensical erorr check for an existing non-error.

You are making the same mistake I did when I saw the patch.

This is the _MTRR_ setting, not the microcode loading.

They both had the same issues with HT - and the microcode fix was indeed
just to make sure that the microcode hadn't already been loaded (together
with some locking).

The Intel MTRR patch is similar - add some locking, and add some logic to
just not do it on the right CPU (you're _not_ supposed to read to see if
you are writing the same value: MTRR's can at least in theory have
side-effects, so it's not the same check as for the microcode update).

		Linus