Re: [PATCH v8 21/22] TEST(do-not-upstream): fake qemu-virt PMU events for cdeleg counter-mask testing

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The patch injects non-existent fake PMU events for testing directly into a production driver, polluting the sysfs UAPI and userspace ABI.
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commit 4ecbb9bba705eb0cbe075ec61ec799a9e140a5fc
Author: Atish Patra <atishp@meta.com>

TEST(do-not-upstream): fake qemu-virt PMU events for cdeleg counter-mask testing

This commit adds fake PMU events to the RISC-V SBI PMU driver to exercise
counter-delegation allocation and counter-mask constraints in QEMU.

> diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
> --- a/drivers/perf/riscv_pmu_sbi.c
> +++ b/drivers/perf/riscv_pmu_sbi.c
[ ... ]
> @@ -499,6 +505,9 @@ static struct attribute *qemu_virt_event_group[] = {
>  	RVPMU_EVENT_ATTR_PTR(dTLB_load_miss),
>  	RVPMU_EVENT_ATTR_PTR(dTLB_store_miss),
>  	RVPMU_EVENT_ATTR_PTR(iTLB_load_miss),
> +	RVPMU_EVENT_ATTR_PTR(fake_any),
> +	RVPMU_EVENT_ATTR_PTR(fake_ctr3),
> +	RVPMU_EVENT_ATTR_PTR(fake_ctr34),

[Severity: Medium]
Even though this patch is explicitly marked as a test that is not meant for
upstream, does unconditionally appending these fake events to
qemu_virt_event_group pollute the sysfs UAPI?

Because they are added directly to the group array, tools interacting with
sysfs will see these non-existent hardware PMU events exposed as part of the
public userspace ABI. Could this logic be exercised using a dedicated test
framework rather than injecting fake test events into a production driver?

>  	NULL,
>  };

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Sashiko AI review · https://sashiko.dev/#/patchset/20260701-counter_delegation-v8-0-7909f863a645@meta.com?part=21