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From:   Rob Herring <robh@kernel.org>
Date:   Wed, 7 Dec 2022 13:56:52 -0600
Message-ID: <CAL_JsqLfZVrwFgYDwA9mz3FPp3jf0r5OOajTJ=7QvwE8P8UKyw@mail.gmail.com>
Subject: Re: [PATCH v3 7/8] perf: Add perf_event_attr::config3
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Will Deacon <will@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Ingo Molnar <mingo@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Marc Zyngier <maz@kernel.org>,
        Oliver Upton <oliver.upton@linux.dev>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        James Morse <james.morse@arm.com>,
        Alexandru Elisei <alexandru.elisei@arm.com>,
        kvmarm@lists.linux.dev, linux-perf-users@vger.kernel.org,
        linux-kernel@vger.kernel.org, James Clark <james.clark@arm.com>,
        Mark Brown <broonie@kernel.org>,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu
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On Tue, Dec 6, 2022 at 10:28 AM Mark Rutland <mark.rutland@arm.com> wrote:
>
> Peter, it looks like this series is blocked on the below now; what would you
> prefer out of:
>
> (a) Take this as is, and look add adding additional validation on top.
>
> (b) Add some flag to indicate a PMU driver supports config3, and have the core
>     code check that, but leave the existing fields as-is for now (and hopefully
>     follow up with further validation later for the existing fields).

That looks something like this:

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 853f64b6c8c2..845162b152ea 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -286,6 +286,7 @@ struct perf_event;
 #define PERF_PMU_CAP_NO_EXCLUDE                        0x0080
 #define PERF_PMU_CAP_AUX_OUTPUT                        0x0100
 #define PERF_PMU_CAP_EXTENDED_HW_TYPE          0x0200
+#define PERF_PMU_CAP_CONFIG3                   0x0400

 struct perf_output_handle;

diff --git a/kernel/events/core.c b/kernel/events/core.c
index aefc1e08e015..4414ae64432a 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11314,6 +11314,9 @@ static int perf_try_init_event(struct pmu
*pmu, struct perf_event *event)
                    event_has_any_exclude_flag(event))
                        ret = -EINVAL;

+               if (!(pmu->capabilities & PERF_PMU_CAP_CONFIG3) &&
event->attr.config3)
+                       ret = -EINVAL;
+
                if (ret && event->destroy)
                        event->destroy(event);
        }