Re: [PATCH] kmemcheck: disable fast string operations on P4 CPUs

H. Peter Anvin
2009-02-22T03:14:16Z

Vegard Nossum wrote:
> This patch may allow us to remove the REP emulation code from
> kmemcheck.

> +#ifdef CONFIG_KMEMCHECK
> + /*
> + * P4s have a "fast strings" feature which causes single-
> + * stepping REP instructions to only generate a #DB on
> + * cache-line boundaries.
> + *
> + * Ingo Molnar reported a Pentium D (model 6) and a Xeon
> + * (model 2) with the same problem.
> + */
> + if (c->x86 == 15) {

If this is supposed to refer to the Intel P4 core, you should exclude
the post-P4 cores that also have x86 == 15 (e.g. Core 2 and Core i7).
If those are affected, too, they should be mentioned in the comment.

-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.