Re: [PATCH V3 1/3] perf tools: enable LBR call stack support

[Namhyung Kim <namhyung@kernel.org>]

On Fri, 14 Nov 2014 08:44:10 -0500, kan liang wrote:
> From: Kan Liang <kan.liang@intel.com>
>
> Currently, there are two call chain recording options, fp and dwarf.
> Haswell has a new feature that utilizes the existing LBR facility to
> record call chains. So it provides the third options to record call
> chain. This patch enables the lbr call stack support.
>
> LBR call stack has some limitations. It reuses current LBR facility, so
> LBR call stack and branch record can not be enabled at the same time. It
> is only available for user callchain.
> However, LBR call stack can work on the user app which doesn't have
> frame-pointer or dwarf debug info compiled. It is a good alternative
> when nothing else works.

So this is only for Haswell or later, right?  What if user gives it to
the other CPUs - is it fail or ignore silently?  I think we need to warn
user about it more kindly..

Thanks,
Namhyung