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SubjectRE: [PATCH v3 2/3] perf: add arm64 smmuv3 pmu driver
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> -----Original Message-----
> From: Robin Murphy [mailto:robin.murphy@arm.com]
> Sent: 02 October 2018 17:35
> To: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>; Shameerali
> Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>;
> lorenzo.pieralisi@arm.com
> Cc: mark.rutland@arm.com; vkilari@codeaurora.org;
> neil.m.leeder@gmail.com; pabba@codeaurora.org; John Garry
> <john.garry@huawei.com>; will.deacon@arm.com; rruigrok@codeaurora.org;
> Linuxarm <linuxarm@huawei.com>; linux-acpi@vger.kernel.org; linux-arm-
> kernel@lists.infradead.org; Guohanjun (Hanjun Guo)
> <guohanjun@huawei.com>; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v3 2/3] perf: add arm64 smmuv3 pmu driver
>
> On 02/10/18 17:19, Jean-Philippe Brucker wrote:
> > On 02/10/2018 15:11, Jean-Philippe Brucker wrote:
> >>> + cfgr = readl_relaxed(smmu_pmu->reg_base + SMMU_PMCG_CFGR);
> >
> > Something I missed previously: when SMMU_PMCG_CFGR.SID_FILTER_TYPE
> is 1,
> > filtering for all counters is configured by SMMU_PMCG_SMR0 and
> > SMMU_PMCG_EVTYPER0 (instead of having one separate filter per counter).
>
> Oh, I hadn't even noticed it had that mode as well...

Thanks Jean. Missed that completely.

> > In that mode with your patch, if the user applies a filter to the first
> > event in the list passed to perf, it will be applied to all events.
> > Filter applied on any subsequent event will be ignored. Could we make
> > this more explicit? Maybe in the probe print that the PMCG is
> > global-filtering, and when attempting to apply a filter to something
> > else than EVCNTR0, return an error?
>
> FWIW filtering is always per-counter-group on the SMMUv2 PMU, and it's
> actually pretty straightforward to cope with - pmu->add() just needs to
> reject the event if one with an incompatible configuration is already
> scheduled, so perf core handles it much like having more events than
> counters, by rotating the mutually-exclusive sets.

I will take a look and address this in next version.

Thanks,
Shameer
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