Re: [PATCH] perf_events: improve DS/BTS/PEBS buffer allocation

Peter Zijlstra
2010-09-13T15:17:15Z

On Mon, 2010-09-13 at 17:13 +0200, Stephane Eranian wrote:
> > For now I think you can not do this. vmalloc'ed memory can't be safely
> > accessed from NMIs in x86 because that might fault. And faults from NMIs
> > are not supported. They cause very bad things: return from fault calls
> > iret which reenables NMI, so NMI can nest but in the meantime there is
> > only one NMI stack, so that gets quickly messed up.
> >
> What kind of faults are you talking about here? TLB faults?

Page faults. vmalloc pte setup is lazy.