linux-kernel - Re: [PATCH v5 20/21] tools/perf: Pass the Counter constraint values in the pmu events

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Message-ID: <9d827020-ee6c-40c2-a83d-7eb9a00f8aa8@linux.dev>
Date: Tue, 22 Apr 2025 17:17:56 -0700
From: Atish Patra <atish.patra@...ux.dev>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Ian Rogers <irogers@...gle.com>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Conor Dooley <conor@...nel.org>, devicetree@...r.kernel.org,
 kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org,
 linux-arm-kernel@...ts.infradead.org, linux-perf-users@...r.kernel.org,
 Jiri Olsa <jolsa@...nel.org>, Paul Walmsley <paul.walmsley@...ive.com>,
 Palmer Dabbelt <palmer@...belt.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Anup Patel <anup@...infault.org>,
 Atish Patra <atishp@...shpatra.org>, Will Deacon <will@...nel.org>,
 Mark Rutland <mark.rutland@....com>, Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...hat.com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH v5 20/21] tools/perf: Pass the Counter constraint values
 in the pmu events

On 3/27/25 12:36 PM, Atish Patra wrote:
> RISC-V doesn't have any standard event to counter mapping discovery
> mechanism in the ISA. The ISA defines 29 programmable counters and
> platforms can choose to implement any number of them and map any
> events to any counters. Thus, the perf tool need to inform the driver
> about the counter mapping of each events.
> 
> The current perf infrastructure only parses the 'Counter' constraints
> in metrics. This patch extends that to pass in the pmu events so that
> any driver can retrieve those values via perf attributes if defined
> accordingly.
> 

Hi Ian/Arnaldo/Namhyung,
Any thoughts on this patch ? Please let me know if there are any other 
better approaches to pass the counter constraints to the driver ?

The RISC-V pmu driver maps the attr.config2 with counterid_mask value
so that driver can parse the counter restrictions.


> Signed-off-by: Atish Patra <atishp@...osinc.com>
> ---
>   tools/perf/pmu-events/jevents.py | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/tools/perf/pmu-events/jevents.py b/tools/perf/pmu-events/jevents.py
> index fdb7ddf093d2..f9f274678a32 100755
> --- a/tools/perf/pmu-events/jevents.py
> +++ b/tools/perf/pmu-events/jevents.py
> @@ -274,6 +274,11 @@ class JsonEvent:
>           return fixed[name.lower()]
>         return event
>   
> +    def counter_list_to_bitmask(counterlist):
> +      counter_ids = list(map(int, counterlist.split(',')))
> +      bitmask = sum(1 << pos for pos in counter_ids)
> +      return bitmask
> +
>       def unit_to_pmu(unit: str) -> Optional[str]:
>         """Convert a JSON Unit to Linux PMU name."""
>         if not unit or unit == "core":
> @@ -427,6 +432,10 @@ class JsonEvent:
>         else:
>           raise argparse.ArgumentTypeError('Cannot find arch std event:', arch_std)
>   
> +    if self.counters['list']:
> +      bitmask = counter_list_to_bitmask(self.counters['list'])
> +      event += f',counterid_mask={bitmask:#x}'
> +
>       self.event = real_event(self.name, event)
>   
>     def __repr__(self) -> str:
>