• Mark Rutland's avatar
    perf/arm: Special-case hetereogeneous CPUs · 5101ef20
    Mark Rutland authored
      26657848 ("perf/core: Verify we have a single perf_hw_context PMU")
    forcefully prevents multiple PMUs from sharing perf_hw_context, as this
    generally doesn't make sense. It is a common bug for uncore PMUs to
    use perf_hw_context rather than perf_invalid_context, which this detects.
    However, systems exist with heterogeneous CPUs (and hence heterogeneous
    HW PMUs), for which sharing perf_hw_context is necessary, and possible
    in some limited cases.
    To make this work we have to perform some gymnastics, as we did in these
      66eb579e ("perf: allow for PMU-specific event filtering")
      c904e32a ("arm: perf: filter unschedulable events")
    To allow those systems to work, we must allow PMUs for heterogeneous
    CPUs to share perf_hw_context, though we must still disallow sharing
    otherwise to detect the common misuse of perf_hw_context.
    This patch adds a new PERF_PMU_CAP_HETEROGENEOUS_CPUS for this, updates
    the core logic to account for this, and makes use of it in the arm_pmu
    code that is used for systems with heterogeneous CPUs. Comments are
    added to make the rationale clear and hopefully avoid accidental abuse.
    Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Catalin Marinas <catalin.marinas@arm.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephane Eranian <eranian@google.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Vince Weaver <vincent.weaver@maine.edu>
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: linux-arm-kernel@lists.infradead.org
    Link: http://lkml.kernel.org/r/20160426103346.GA20836@leverpostejSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
arm_pmu.c 25.1 KB