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Date: Fri, 8 Aug 2014 09:04:13 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Andi Kleen <andi@...stfloor.org> Cc: kan.liang@...el.com, linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com> Subject: Re: [PATCH] perf, x86: Fix :pp without LBR On Thu, Aug 07, 2014 at 05:08:54PM -0700, Andi Kleen wrote: > From: Andi Kleen <ak@...ux.intel.com> > > This fixes a side effect of Kan's earlier patch to probe the LBRs at boot > time. Normally when the LBRs are disabled cycles:pp is disabled too. > So for example cycles:pp doesn't work. > > However this is not needed with PEBSv2 and later (Haswell) because > it does not need LBRs to correct the IP-off-by-one. > > So add an extra check for PEBSv2 that also allows :pp > > Signed-off-by: Andi Kleen <ak@...ux.intel.com> > --- > arch/x86/kernel/cpu/perf_event.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c > index 2879ecd..0646d3b 100644 > --- a/arch/x86/kernel/cpu/perf_event.c > +++ b/arch/x86/kernel/cpu/perf_event.c > @@ -387,7 +387,7 @@ int x86_pmu_hw_config(struct perf_event *event) > precise++; > > /* Support for IP fixup */ > - if (x86_pmu.lbr_nr) > + if (x86_pmu.lbr_nr || x86_pmu.intel_cap.pebs_format >= 2) > precise++; Thanks -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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