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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?


> 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
> --
> -- Speaking for myself only

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