lkml.org 
[lkml]   [2016]   [Jan]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] x86: static_cpu_has_safe: discard dynamic check after init
From
Date
On January 18, 2016 3:05:54 PM PST, Borislav Petkov <bp@suse.de> wrote:
>On Mon, Jan 18, 2016 at 11:45:18AM -0800, H. Peter Anvin wrote:
>> I think the two-byte optimization is the real issue if there is one
>at
>> all.
>
>Well, we do optimize the jumps for a couple releases now, see
>recompute_jump(). So we would always get the short JMP, if made
>possible
>by how gcc lays out the code so that the target is not far away. If the
>JMP to the dynamic branch doesn't get nopped out anyway, that is.
>
>We have "debug-alternative" to dump exactly what happens during
>patching.
>
>> I don't care about the inittext, and unless I'm misremembering
>> completely altinstructions also get ejected.
>
>Ah yes, they do.
>
>> So I don't personally object to killing off the unsafe variant.
>
>Ok.

The optimization has always been there, the question is how often it actually kicks in.
--
Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.

\
 
 \ /
  Last update: 2016-01-19 00:21    [W:0.094 / U:0.180 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site