[PATCH 4.9 145/240] powerpc/perf: Fix PMU constraint check for EBB events

Greg Kroah-Hartman
2021-05-20T11:18:44Z

From: Athira Rajeev <atrajeev@linux.vnet.ibm.com>

[ Upstream commit 10f8f96179ecc7f69c927f6d231f6d02736cea83 ]

The power PMU group constraints includes check for EBB events to make
sure all events in a group must agree on EBB. This will prevent
scheduling EBB and non-EBB events together. But in the existing check,
settings for constraint mask and value is interchanged. Patch fixes the
same.

Before the patch, PMU selftest "cpu_event_pinned_vs_ebb_test" fails with
below in dmesg logs. This happens because EBB event gets enabled along
with a non-EBB cpu event.

[35600.453346] cpu_event_pinne[41326]: illegal instruction (4)
at 10004a18 nip 10004a18 lr 100049f8 code 1 in
cpu_event_pinned_vs_ebb_test[10000000+10000]

Test results after the patch:

$ ./pmu/ebb/cpu_event_pinned_vs_ebb_test
test: cpu_event_pinned_vs_ebb
tags: git_version:v5.12-rc5-93-gf28c3125acd3-dirty
Binding to cpu 8
EBB Handler is at 0x100050c8
read error on event 0x7fffe6bd4040!
PM_RUN_INST_CMPL: result 9872 running/enabled 37930432
success: cpu_event_pinned_vs_ebb

This bug was hidden by other logic until commit 1908dc911792 (perf:
Tweak perf_event_attr::exclusive semantics).

Fixes: 4df489991182 ("powerpc/perf: Add power8 EBB support")
Reported-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
[mpe: Mention commit 1908dc911792]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1617725761-1464-1-git-send-email-atrajeev@linux.vnet.ibm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/powerpc/perf/isa207-common.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/perf/isa207-common.c b/arch/powerpc/perf/isa207-common.c
index 7592a6491a9a..2d3557406424 100644
--- a/arch/powerpc/perf/isa207-common.c
+++ b/arch/powerpc/perf/isa207-common.c
@@ -139,8 +139,8 @@ ebb_bhrb:
* EBB events are pinned & exclusive, so this should never actually
* hit, but we leave it as a fallback in case.
*/
- mask |= CNST_EBB_VAL(ebb);
- value |= CNST_EBB_MASK;
+ mask |= CNST_EBB_MASK;
+ value |= CNST_EBB_VAL(ebb);

*maskp = mask;
*valp = value;
--
2.30.2