Re: [PATCH] x86_64, asm: Work around AMD SYSRET SS descriptor attribute issue

Linus Torvalds
2015-04-27T18:14:20Z

On Mon, Apr 27, 2015 at 9:40 AM, Borislav Petkov <bp@alien8.de> wrote:
>
> Either way, the NOPs-version is faster and I'm running the test with the
> F16h-specific NOPs to see how they perform.

Btw, please don't use the "more than three 66h overrides" version.
Sure, that's what the optimization manual suggests if you want
single-instruction decode for all sizes up to 15 bytes, but I think
we're better off with the two-nop case for sizes 12-15) (4-byte nop
followed by 8-11 byte nop).

Because the "more than three 66b prefixes" really performs abysmally
on some cores, iirc.

Linus