lkml.org 
[lkml]   [2014]   [Jul]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] perf/x86/intel: ignore CondChgd bit to avoid false NMI handling
On Mon, Jun 30, 2014 at 03:22:24PM -0700, Andi Kleen wrote:
> >
> > I'm also interested in the behaviour of CondChgd bit on Ivy Bridge processors.
>
> The intended meaning of CondChgd is that a hardware debugger has taken over the
> PMU. It shouldn't really be set in other circumstances.

Interesting. My concern is we have customers that can soft reboot a
machine and have this bit accidentally be enabled. I am pretty sure they
do not have a hardware debugger attached (I would have to double check).
Is there other ways this can be set?

Cheers,
Don

>
> I think right now for perf it would be best to just ignore it.
>
> In theory could stop using the PMU, but if some BIOS set it it would
> completely disable perf there. So better to just ignore it.
>
> -Andi
>
> --
> ak@linux.intel.com -- Speaking for myself only


\
 
 \ /
  Last update: 2014-07-01 17:41    [W:0.052 / U:10.132 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site