lkml.org 
[lkml]   [2018]   [Jan]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 4/8] x86/spec_ctrl: Add sysctl knobs to enable/disable SPEC_CTRL feature
On Fri, Jan 05, 2018 at 07:12:12PM -0800, Dave Hansen wrote:
> On 01/05/2018 06:12 PM, Tim Chen wrote:
> > .macro ENABLE_IBRS
> > - ALTERNATIVE "jmp .Lskip_\@", "", X86_FEATURE_SPEC_CTRL
> > + testl $1, dynamic_ibrs
> > + jz .Lskip_\@
>
> There was an earlier suggestion to use STATIC_JUMP_IF_... here. That's

Yes, and thanks for Cc'ing me... :/

> a good suggestion, but we encountered some issues with it either
> crashing the kernel at boot or not properly turning on/off.
>
> We would love to do that minor really soon, but we figured everyone
> would rather see this version than wait for us to debug such a minor tweak.

Its not minor, you need that LFENCE without it. Which makes the whole
thing unconditionally expensive, which sucks.

\
 
 \ /
  Last update: 2018-01-14 23:17    [W:0.286 / U:0.444 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site