Re: [PATCH v2 1/5] alpha/perf: pass PERFMON_CMD_LOGGING_ALL to the logging options call

[Magnus Lindholm]

Hi Matt,

On Fri, Oct 30, 2026 at 5:04 AM Matt Turner <mattst88@xxxxxxxxx> wrote:
>
> alpha_pmu_enable() passes EV67_PCTR_MODE_AGGREGATE to
> PERFMON_CMD_LOGGING_OPTIONS. That constant is the counting mode bit for
> PCTR_CTL, which belongs in the PERFMON_CMD_DESIRED_EVENTS argument. The
> logging options call takes a flag in bit 0 where 0 means "count all
> processes". It works only because EV67_PCTR_MODE_AGGREGATE happens to be
> 0.
>
> Table E-18 of the Alpha Architecture Reference Manual gives bit 0 the
> opposite sense, but the PALcode in the ES40 and ES47 firmware agrees
> with the above: it sets I_CTL[SPCE], which enables counting for all
> processes, unless bit 0 is set. Linux never sets the PME bit in the
> PCB, so if 0 meant "selected processes only", nothing would be counted.
>
> Add a name for that argument and pass it instead. No functional change.
>
> Signed-off-by: Matt Turner <mattst88@xxxxxxxxx>
> ---
>  arch/alpha/include/asm/wrperfmon.h | 2 ++
>  arch/alpha/kernel/perf_event.c     | 2 +-
>  2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/alpha/include/asm/wrperfmon.h b/arch/alpha/include/asm/wrperfmon.h
> index c97b82a1f7db..1fa9bc813263 100644
> --- a/arch/alpha/include/asm/wrperfmon.h
> +++ b/arch/alpha/include/asm/wrperfmon.h
> @@ -23,6 +23,8 @@
>  #define PERFMON_CMD_I_STAT 8
>  #define PERFMON_CMD_PMPC 9
>
> +/* PERFMON_CMD_LOGGING_OPTIONS arguments */
> +#define PERFMON_CMD_LOGGING_ALL 0
>
>  /* EV5/EV56/PCA56 Counters */
>  #define EV5_PCTR_0 (1UL<<0)
> diff --git a/arch/alpha/kernel/perf_event.c b/arch/alpha/kernel/perf_event.c
> index a3eaab094ece..2d9383425357 100644
> --- a/arch/alpha/kernel/perf_event.c
> +++ b/arch/alpha/kernel/perf_event.c
> @@ -728,7 +728,7 @@ static void alpha_pmu_enable(struct pmu *pmu)
>                 maybe_change_configuration(cpuc);
>
>                 /* Start counting the desired events. */
> -               wrperfmon(PERFMON_CMD_LOGGING_OPTIONS, EV67_PCTR_MODE_AGGREGATE);
> +               wrperfmon(PERFMON_CMD_LOGGING_OPTIONS, PERFMON_CMD_LOGGING_ALL);
>                 wrperfmon(PERFMON_CMD_DESIRED_EVENTS, cpuc->config);
>                 wrperfmon(PERFMON_CMD_ENABLE, cpuc->idx_mask);
>         }
>
> --
> 2.55.0
>

Thanks for the update, tested as part of the v2 series on my
AlphaServer ES40. Looks good!

Reviewed-by: Magnus Lindholm <linmag7@xxxxxxxxx>
Tested-by: Magnus Lindholm <linmag7@xxxxxxxxx>