linux-kernel - [PATCH 5.8 094/633] perf/x86/intel/uncore: Reduce the number of CBOX counters

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Date:   Tue, 27 Oct 2020 14:47:17 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Kan Liang <kan.liang@...ux.intel.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.8 094/633] perf/x86/intel/uncore: Reduce the number of CBOX counters

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

[ Upstream commit ee139385432e919f4d1f59b80edbc073cdae1391 ]

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20200925134905.8839-3-kan.liang@linux.intel.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 300937cc8795b..3b70c2ff177c0 100644
--- a/arch/x86/events/intel/uncore_snb.c
+++ b/arch/x86/events/intel/uncore_snb.c
@@ -314,7 +314,7 @@ 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,
-- 
2.25.1