linux-kernel - Re: [PATCH] perf/arm_smmuv3: Omit the two judgements which done in framework

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Date: Fri, 9 Feb 2024 16:09:06 +0000
From: Will Deacon <will@...nel.org>
To: "JiaLong.Yang" <jialong.yang@...ngroup.cn>
Cc: Mark Rutland <mark.rutland@....com>, shenghui.qu@...ngroup.cn,
	ke.zhao@...ngroup.cn, zhijie.ren@...ngroup.cn,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf/arm_smmuv3: Omit the two judgements which done in
 framework

On Thu, Dec 21, 2023 at 05:38:01PM +0800, JiaLong.Yang wrote:
> 'event->attr.type != event->pmu->type' has been done in
> core.c::perf_init_event() ,core.c::perf_event_modify_attr(), etc.
>
> This PMU is an uncore one. The core framework has disallowed
> uncore-task events. So the judgement to event->cpu < 0 is no mean.

It would be great to refer to the changes which added those checks to
the perf core code. From reading the code myself, I can't convince myself
that perf_try_init_event() won't call into the driver.

> 
> The two judgements have been done in kernel/events/core.c
> 
> Signed-off-by: JiaLong.Yang <jialong.yang@...ngroup.cn>
> ---
>  drivers/perf/arm_smmuv3_pmu.c | 8 --------
>  1 file changed, 8 deletions(-)

It looks like _many_ perf drivers have these checks, so if they really
aren't needed, we can clean this up bveyond SMMU. However, as I said
above, I'm not quite convinced we can drop them.

Will