linux-kernel - Re: [PATCH 19/19] perf: Garbage-collect event

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Message-ID: <271daf71-3c57-49a5-a65f-c58ac670864f@arm.com>
Date: Tue, 19 Aug 2025 14:25:45 +0100
From: Robin Murphy <robin.murphy@....com>
To: peterz@...radead.org, mingo@...hat.com, will@...nel.org,
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Subject: Re: [PATCH 19/19] perf: Garbage-collect event_init checks

On 13/08/2025 6:01 pm, Robin Murphy wrote:
[...]
> diff --git a/arch/x86/events/intel/uncore.c b/arch/x86/events/intel/uncore.c
> index 297ff5adb667..98ffab403bb4 100644
> --- a/arch/x86/events/intel/uncore.c
> +++ b/arch/x86/events/intel/uncore.c
> @@ -731,24 +731,11 @@ static int uncore_pmu_event_init(struct perf_event *event)
>   	struct hw_perf_event *hwc = &event->hw;
>   	int ret;
>   
> -	if (event->attr.type != event->pmu->type)
> -		return -ENOENT;
> -
>   	pmu = uncore_event_to_pmu(event);
>   	/* no device found for this pmu */
>   	if (!pmu->registered)
>   		return -ENOENT;
>   
> -	/* Sampling not supported yet */
> -	if (hwc->sample_period)
> -		return -EINVAL;
> -
> -	/*
> -	 * Place all uncore events for a particular physical package
> -	 * onto a single cpu
> -	 */
> -	if (event->cpu < 0)
> -		return -EINVAL;

Oopsie, I missed that this isn't just the usual boilerplate as the 
comment kind of implies, but is also necessary to prevent the 
uncore_pmu_to_box() lookup going wrong (since the core code won't reject 
a task-bound event until later). I'll put this back with an updated 
comment for v2 (and double-check everything else again...), thanks LKP!

Robin.


>   	box = uncore_pmu_to_box(pmu, event->cpu);
>   	if (!box || box->cpu < 0)
>   		return -EINVAL;