• Mark Rutland's avatar
    perf pmu: Unbreak perf record for arm/arm64 with events with explicit PMU · 66ec1191
    Mark Rutland authored
    Currently, perf record is broken on arm/arm64 systems when the PMU is
    specified explicitly as part of the event, e.g.
    
    $ ./perf record -e armv8_cortex_a53/cpu_cycles/u true
    
    In such cases, perf record fails to open events unless
    perf_event_paranoid is set to -1, even if the PMU in question supports
    mode exclusion. Further, even when perf_event_paranoid is toggled, no
    samples are recorded.
    
    This is an unintended side effect of commit:
    
      e3ba76de ("perf tools: Force uncore events to system wide monitoring)
    
    ... which assumes that if a PMU has an associated cpu_map, it is an
    uncore PMU, and forces events for such PMUs to be system-wide.
    
    This is not true for arm/arm64 systems, which can have heterogeneous
    CPUs. To account for this, multiple CPU PMUs are exposed, each with a
    "cpus" field under sysfs, which the perf tool parses into a cpu_map. ARM
    PMUs do not have a "cpumask" file, and only have a "cpus" file. For the
    gory details as to why, see commit:
    
     7e3fcffe ("perf pmu: Support alternative sysfs cpumask")
    
    Given all of this, we can instead identify uncore PMUs by explicitly
    checking for a "cpumask" file, and restore arm/arm64 PMU support back to
    a working state. This patch does so, adding a new perf_pmu::is_uncore
    field, and splitting the existing cpumask parsing so that it can be
    reused.
    Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
    Tested-by Will Deacon <will.deacon@arm.com>
    Acked-by: default avatarJiri Olsa <jolsa@kernel.org>
    Cc: Adrian Hunter <adrian.hunter@intel.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: David Ahern <dsahern@gmail.com>
    Cc: Namhyung Kim <namhyung@kernel.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: 4.12+ <stable@vger.kernel.org>
    Fixes: e3ba76de ("perf tools: Force uncore events to system wide monitoring)
    Link: http://lkml.kernel.org/r/1507315102-5942-1-git-send-email-mark.rutland@arm.comSigned-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
    66ec1191
pmu.c 28 KB