[tip:perf/core] perf/x86: Fix :pp without LBR

[tip-bot for Andi Kleen]

Commit-ID:  03de874aa76ac0adcf6f56ebf3de623d09a5dde3
Gitweb:     http://git.kernel.org/tip/03de874aa76ac0adcf6f56ebf3de623d09a5dde3
Author:     Andi Kleen <ak@xxxxxxxxxxxxxxx>
AuthorDate: Thu, 7 Aug 2014 17:08:54 -0700
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 13 Aug 2014 07:51:12 +0200

perf/x86: Fix :pp without LBR

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@xxxxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: kan.liang@xxxxxxxxx
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1407456534-15747-1-git-send-email-andi@xxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 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++;
 		}
 
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