Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge

Peter Zijlstra
2012-06-13T15:37:59Z

On Wed, 2012-06-13 at 07:00 -0700, H. Peter Anvin wrote:
> On 06/13/2012 01:38 AM, Peter Zijlstra wrote:
> > On Tue, 2012-06-12 at 13:58 -0700, H. Peter Anvin wrote:
> >> even things like Nehalem + Westmere in the same system
> >
> > Uhm,.. how well do you expect Linux to run on a franken-system like
> > that? I'm pretty sure perf will malfunction in such a setup.
> >
>
> perf might, but I have seen such frankensystems in the field and they
> work (although I haven't seen that particular combo, I have to admit.)

Thing is, if we boot on the wsm, perf could fault the system with
nonexistent MSR accesses, if we boot on the nhm worst is wrong numbers I
think.

I'm not really inclined to 'fix' this.. the best I'm willing to accept
is a patch that would detect this situation and simply disable all
hardware perf support for the platform.