linux-kernel - [PATCH 3/3] perf/x86/intel/uncore: Reduce the number of CBOX counters

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Message-Id: <20200925134905.8839-3-kan.liang@linux.intel.com>
Date:   Fri, 25 Sep 2020 06:49:05 -0700
From:   kan.liang@...ux.intel.com
To:     peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     ak@...ux.intel.com, asit.k.mallick@...el.com,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: [PATCH 3/3] perf/x86/intel/uncore: Reduce the number of CBOX counters

From: Kan Liang <kan.liang@...ux.intel.com>

An oops is triggered by the fuzzy test.

[  327.853081] unchecked MSR access error: RDMSR from 0x70c at rIP:
0xffffffffc082c820 (uncore_msr_read_counter+0x10/0x50 [intel_uncore])
[  327.853083] Call Trace:
[  327.853085]  <IRQ>
[  327.853089]  uncore_pmu_event_start+0x85/0x170 [intel_uncore]
[  327.853093]  uncore_pmu_event_add+0x1a4/0x410 [intel_uncore]
[  327.853097]  ? event_sched_in.isra.118+0xca/0x240

There are 2 GP counters for each CBOX, but the current code claims 4
counters. Accessing the invalid registers triggers the oops.

Fixes: 6e394376ee89 ("perf/x86/intel/uncore: Add Intel Icelake uncore support")
Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
---
 arch/x86/events/intel/uncore_snb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/uncore_snb.c b/arch/x86/events/intel/uncore_snb.c
index 2bdfcf80b434..de3d9621b694 100644
--- a/arch/x86/events/intel/uncore_snb.c
+++ b/arch/x86/events/intel/uncore_snb.c
@@ -325,7 +325,7 @@ static struct intel_uncore_ops icl_uncore_msr_ops = {
 
 static struct intel_uncore_type icl_uncore_cbox = {
 	.name		= "cbox",
-	.num_counters   = 4,
+	.num_counters   = 2,
 	.perf_ctr_bits	= 44,
 	.perf_ctr	= ICL_UNC_CBO_0_PER_CTR0,
 	.event_ctl	= SNB_UNC_CBO_0_PERFEVTSEL0,
-- 
2.17.1