Re: [PATCH RFC 0/7] perf pmu-events: Support event aliasing for system PMUs

From: Will Deacon
Date: Tue Feb 18 2020 - 07:57:36 EST

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.