Re: [PATCH] x86, cpu: Fix X86_FEATURE_NOPL
From: Linus Torvalds
Date: Mon Oct 04 2010 - 16:48:28 EST
On Mon, Oct 4, 2010 at 12:31 AM, Borislav Petkov <bp@xxxxxxxxx> wrote:
>
> ba0593bf553c450a03dbc5f8c1f0ff58b778a0c8 cleared the aforementioned
> cpuid bit only on 32-bit due to various problems with Virtual PC. This
> somehow got lost during the 32- + 64-bit merge so restore the feature
> bit on 64-bit. For that, set it explicitly for non-constant arguments of
> cpu_has(). Update comment for future reference.
I don't think this is right.
The cpu_has() logic depends not on x86-64, but on X86_P6_NOP.
Which has
depends on X86_64
depends on (MCORE2 || MPENTIUM4 || MPSC)
as its config rules, not just X86_64.
So I think your patch is bogus. It makes the current situation even
_more_ confusing than it is.
So what is it? Should we get rid of that odd X86_P6_NOP thing
entirely? Or should we use it consistently for the "this machine has
NOPL"? Should we always use P6_NOP for x86-64 and just remove the
"MCORE2 || MPENTIUM4 || MPSC" thing?
Whatever we do, I don't think this patch is the right one.
Linus
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