linux-kernel - [PATCH 5.4 187/244] powerpc/perf: Fix PMU constraint check for EBB events

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Message-Id: <20210512144748.982503202@linuxfoundation.org>
Date:   Wed, 12 May 2021 16:49:18 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>,
        Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.4 187/244] powerpc/perf: Fix PMU constraint check for EBB events

From: Athira Rajeev <atrajeev@...ux.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@...onical.com>
Signed-off-by: Athira Rajeev <atrajeev@...ux.vnet.ibm.com>
[mpe: Mention commit 1908dc911792]
Signed-off-by: Michael Ellerman <mpe@...erman.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@...nel.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 0b5c8f4fbdbf..944180f55a3c 100644
--- a/arch/powerpc/perf/isa207-common.c
+++ b/arch/powerpc/perf/isa207-common.c
@@ -363,8 +363,8 @@ 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