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Subject[tip: perf/core] perf/x86/intel/uncore: Reduce the number of CBOX counters
The following commit has been merged into the perf/core branch of tip:

Commit-ID: ee139385432e919f4d1f59b80edbc073cdae1391
Gitweb: https://git.kernel.org/tip/ee139385432e919f4d1f59b80edbc073cdae1391
Author: Kan Liang <kan.liang@linux.intel.com>
AuthorDate: Fri, 25 Sep 2020 06:49:05 -07:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 29 Sep 2020 09:57:01 +02:00

perf/x86/intel/uncore: Reduce the number of CBOX counters

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@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200925134905.8839-3-kan.liang@linux.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 2bdfcf8..de3d962 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,
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