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SubjectRe: [PATCH v12 2/5] perf: Add a counter for number of user access events in context
On Fri, Dec 03 2021 at 09:58, Rob Herring wrote:
> On Tue, Nov 30, 2021 at 4:57 PM Thomas Gleixner <> wrote:
> I've rewritten it like this:
> On arm64, user space counter access will be controlled differently
> compared to x86. On x86, access in the strictest mode is enabled for all
> tasks in an MM when any event is mmap'ed. For arm64, access is
> explicitly requested for an event and only enabled when the event's
> context is active. This avoids hooks into the arch context switch code
> and gives better control of when access is enabled.
> In order to configure user space access when the PMU is enabled, it is
> necessary to know if any event (currently active or not) in the current
> context has user space accessed enabled. Add a counter similar to other
> counters in the context to avoid walking the event list every time.

Reviewed-by: Thomas Gleixner <>

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