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    SubjectRe: [PATCH RFC 0/7] perf pmu-events: Support event aliasing for system PMUs
    On Fri, Jan 24, 2020 at 10:34:58PM +0800, John Garry wrote:
    > Currently event aliasing for only CPU and uncore PMUs is supported. In
    > fact, only uncore PMUs aliasing for when the uncore PMUs are fixed for a
    > CPU is supported, which may not always be the case for certain
    > architectures.
    >
    > This series adds support for PMU event aliasing for system and other
    > uncore PMUs which are not fixed to a specific CPU.
    >
    > For this, we introduce support for another per-arch mapfile, which maps a
    > particular system identifier to a set of system PMU events for that
    > system. This is much the same as what we do for CPU event aliasing.
    >
    > To support this, we need to change how we match a PMU to a mapfile,
    > whether it should use a CPU or system mapfile. For this we do the
    > following:
    >
    > - For CPU PMU, we always match for the event mapfile based on the CPUID.
    > This has not changed.
    >
    > - For an uncore or system PMU, we match first based on the SYSID (if set).
    > If this fails, then we match on the CPUID.
    >
    > This works for x86, as x86 would not have any system mapfiles for uncore
    > PMUs (and match on the CPUID).
    >
    > Initial reference support is also added for ARM SMMUv3 PMCG (Performance
    > Monitor Event Group) PMU for HiSilicon hip08 platform with only a single
    > event so far - see driver in drivers/perf/arm_smmuv3_pmu.c for that driver.

    Why don't we just expose SMMU_IIDR in the SMMUv3 PMU directory, so that
    you can key off that? I'm nervous about coming up with a global "SYSID"
    when we don't have the ability to standardise anything in that space.

    Will

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