Messages in this thread | | | Date | Thu, 12 Oct 2023 10:05:50 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH] drivers: perf: arm_pmuv3: Update 'pmc_width' based on actual HW event width |
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On Mon, Oct 09, 2023 at 10:07:24AM +0530, Anshuman Khandual wrote: > This updates 'perf_event_mmap_page->pmc_width' based on actual HW event's > width that are currently missing i.e ARMPMU_EVT_63BIT and ARMPMU_EVT_47BIT. > > Cc: Will Deacon <will@kernel.org> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > This applies on v6.6-rc5. > > drivers/perf/arm_pmuv3.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c > index fe4db1831662..94723d00548e 100644 > --- a/drivers/perf/arm_pmuv3.c > +++ b/drivers/perf/arm_pmuv3.c > @@ -1375,6 +1375,10 @@ void arch_perf_update_userpage(struct perf_event *event, > if (userpg->cap_user_rdpmc) { > if (event->hw.flags & ARMPMU_EVT_64BIT) > userpg->pmc_width = 64; > + else if (event->hw.flags & ARMPMU_EVT_63BIT) > + userpg->pmc_width = 63; > + else if (event->hw.flags & ARMPMU_EVT_47BIT) > + userpg->pmc_width = 47;
The PMUv3 driver *never* uses 63-bit or 47-bit counters, so the PMUv3 driver doesn't need this. The ARMPMU_EVT_63BIT and ARMPMU_EVT_47BIT flags are only used by the Apple PMU driver, which doesn't support user access, and similarly doesn't need to handle this.
This code is not necessary as the two new branches can never run. It will also confuse people into thinking the PMUv3 driver can use these widths when it cannot.
NAK to this patch for the reasons above.
Mark
> else > userpg->pmc_width = 32; > } > -- > 2.25.1 >
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