[PATCH 5.10/5.15] perf/arm-cmn: Initialise cmn->cpu earlier

[PATCH 5.10/5.15] perf/arm-cmn: Initialise cmn->cpu earlier

[Robin Murphy]

commit 597704e201068db3d104de3c7a4d447ff8209127 upstream.

For all the complexity of handling affinity for CPU hotplug, what we've
apparently managed to overlook is that arm_cmn_init_irqs() has in fact
always been setting the *initial* affinity of all IRQs to CPU 0, not the
CPU we subsequently choose for event scheduling. Oh dear.

Cc: stable@vger.kernel.org
Fixes: 0ba64770a2f2 ("perf: Add Arm CMN-600 PMU driver")
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
Link: https://lore.kernel.org/r/b12fccba6b5b4d2674944f59e4daad91cd63420b.1747069914.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
[ backport past NUMA changes in 5.17 ]
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
 drivers/perf/arm-cmn.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
index e2a055ba0b7a..cabeff8c944b 100644
--- a/drivers/perf/arm-cmn.c
+++ b/drivers/perf/arm-cmn.c
@@ -1512,6 +1512,7 @@ static int arm_cmn_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	cmn->dev = &pdev->dev;
+	cmn->cpu = raw_smp_processor_id();
 	platform_set_drvdata(pdev, cmn);
 
 	if (has_acpi_companion(cmn->dev))
@@ -1533,7 +1534,6 @@ static int arm_cmn_probe(struct platform_device *pdev)
 	if (err)
 		return err;
 
-	cmn->cpu = raw_smp_processor_id();
 	cmn->pmu = (struct pmu) {
 		.module = THIS_MODULE,
 		.attr_groups = arm_cmn_attr_groups,
-- 
2.39.2.101.g768bb238c484.dirty

Re: [PATCH 5.10/5.15] perf/arm-cmn: Initialise cmn->cpu earlier

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 597704e201068db3d104de3c7a4d447ff8209127

Status in newer kernel trees:
6.15.y | Present (different SHA1: 7b6afec7588f)
6.14.y | Present (different SHA1: 6a7fed0595c2)
6.12.y | Present (different SHA1: fb3a1c1d24ae)
6.6.y | Present (different SHA1: 711b013373b0)
6.1.y | Present (different SHA1: 57c8a80f0b02)
5.15.y | Not found

Note: The patch differs from the upstream commit:
---
1:  597704e201068 < -:  ------------- perf/arm-cmn: Initialise cmn->cpu earlier
-:  ------------- > 1:  ff356633c92f4 perf/arm-cmn: Initialise cmn->cpu earlier
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.10.y       |  Success    |  Success   |
| stable/linux-5.15.y       |  Success    |  Success   |