linux-kernel - Re: [PATCH] driver: perf: arm_pmuv3: Identify 'event->attr.config1' based attributes

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Message-ID: <ZSlKgGtrhsoWCDGT@FVFF77S0Q05N.cambridge.arm.com>
Date:   Fri, 13 Oct 2023 14:47:44 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] driver: perf: arm_pmuv3: Identify 'event->attr.config1'
 based attributes

On Mon, Oct 09, 2023 at 10:47:53AM +0530, Anshuman Khandual wrote:
> This defines macros to identify long and rdpmc attributes which get carried
> inside 'event->attr.config1', thus making the code explicit and clear.
> 
> Cc: Will Deacon <will@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> This applies on v6.6-rc5.
> 
>  drivers/perf/arm_pmuv3.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)

I think this would make sense to do if we also used a common definition of
these bits in the helper functions *and* their format attributes, but as-is
this does nothing to relate the two, and I don't think that it improves
legibility on its own.

Mark.

> diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
> index 94723d00548e..797ffd5a8fed 100644
> --- a/drivers/perf/arm_pmuv3.c
> +++ b/drivers/perf/arm_pmuv3.c
> @@ -298,16 +298,19 @@ PMU_FORMAT_ATTR(event, "config:0-15");
>  PMU_FORMAT_ATTR(long, "config1:0");
>  PMU_FORMAT_ATTR(rdpmc, "config1:1");
>  
> +#define ARM_PMUV3_ATTR_LONG	0x01
> +#define ARM_PMUV3_ATTR_RDPMC	0x02
> +
>  static int sysctl_perf_user_access __read_mostly;
>  
>  static inline bool armv8pmu_event_is_64bit(struct perf_event *event)
>  {
> -	return event->attr.config1 & 0x1;
> +	return event->attr.config1 & ARM_PMUV3_ATTR_LONG;
>  }
>  
>  static inline bool armv8pmu_event_want_user_access(struct perf_event *event)
>  {
> -	return event->attr.config1 & 0x2;
> +	return event->attr.config1 & ARM_PMUV3_ATTR_RDPMC;
>  }
>  
>  static struct attribute *armv8_pmuv3_format_attrs[] = {
> -- 
> 2.25.1
>