linux-kernel - [PATCH] perf/x86: Fix exclusion of BTS and LBR for Goldmont

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Date:   Thu,  8 Dec 2016 16:14:17 -0800
From:   Andi Kleen <andi@...stfloor.org>
To:     peterz@...radead.org
Cc:     linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        alexander.shishkin@...el.com, kan.liang@...el.com,
        stable@...r.kernel.org
Subject: [PATCH] perf/x86: Fix exclusion of BTS and LBR for Goldmont

From: Andi Kleen <ak@...ux.intel.com>

An earlier patch allowed enabling PT and LBR at the same
time on Goldmont. However it also allowed enabling BTS and LBR
at the same time, which is still not supported. Fix this by
bypassing the check only for PT.

Marking for stable because this allows crashing kernels. Also
should be merged for 4.9.

Fixes: ccbebba4c6bf ("erf/x86/intel/pt: Bypass PT vs. LBR exclusivity if the core supports it")
Cc: alexander.shishkin@...el.com
Cc: kan.liang@...el.com
Cc: <stable@...r.kernel.org>
v2: Paint bike shed differently.
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 arch/x86/events/core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index d0efb5cb1b00..baa1eed55e88 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -364,7 +364,7 @@ int x86_add_exclusive(unsigned int what)
 {
 	int i;
 
-	if (x86_pmu.lbr_pt_coexist)
+	if (what == x86_lbr_exclusive_pt && x86_pmu.lbr_pt_coexist)
 		return 0;
 
 	if (!atomic_inc_not_zero(&x86_pmu.lbr_exclusive[what])) {
@@ -387,7 +387,7 @@ fail_unlock:
 
 void x86_del_exclusive(unsigned int what)
 {
-	if (x86_pmu.lbr_pt_coexist)
+	if (what == x86_lbr_exclusive_pt && x86_pmu.lbr_pt_coexist)
 		return;
 
 	atomic_dec(&x86_pmu.lbr_exclusive[what]);
-- 
2.9.3