linux-kernel - [PATCH] x86, perf: Fix Skylake FRONTEND MSR extrareg mask

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Date:	Sat, 18 Jul 2015 07:51:48 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	peterz@...radead.org
Cc:	linux-kernel@...r.kernel.org, eranian@...gle.com,
	Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH] x86, perf: Fix Skylake FRONTEND MSR extrareg mask

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

Stephane pointed out that the extrareg mask was one bit too short.
The bubble width field was truncated by one bit. Fix that here.
Also add some extra comments on the reserved bits inside the event
select code.

Reported-by: Stephane Eranian <eranian@...gle.com>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 arch/x86/kernel/cpu/perf_event_intel.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index caffb41..0861196 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -205,7 +205,11 @@ static struct extra_reg intel_skl_extra_regs[] __read_mostly = {
 	INTEL_UEVENT_EXTRA_REG(0x01b7, MSR_OFFCORE_RSP_0, 0x3fffff8fffull, RSP_0),
 	INTEL_UEVENT_EXTRA_REG(0x01bb, MSR_OFFCORE_RSP_1, 0x3fffff8fffull, RSP_1),
 	INTEL_UEVENT_PEBS_LDLAT_EXTRA_REG(0x01cd),
-	INTEL_UEVENT_EXTRA_REG(0x01c6, MSR_PEBS_FRONTEND, 0x3fff17, FE),
+	/*
+	 * Note the low 8 bits eventsel code is not a continuous field, containing
+	 * some #GPing bits. These are masked out.
+	 */
+	INTEL_UEVENT_EXTRA_REG(0x01c6, MSR_PEBS_FRONTEND, 0x7fff17, FE),
 	EVENT_EXTRA_END
 };
 
-- 
2.4.3

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