Re: [PATCH V7 4/6] arm64/perf: Add branch stack support in struct pmu_hw_events

Mark Rutland
2023-01-12T14:01:18Z

On Thu, Jan 05, 2023 at 08:40:37AM +0530, Anshuman Khandual wrote:
> This adds branch records buffer pointer in 'struct pmu_hw_events' which can
> be used to capture branch records during PMU interrupt. This percpu pointer
> here needs to be allocated first before usage.
>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>

This looks fine, but it's difficult to review this without seeing how its
lifetime is managed, and it feels like this should be folded into a subsequent
patch which manages that.

Thanks,
Mark.

> ---
> include/linux/perf/arm_pmu.h | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/include/linux/perf/arm_pmu.h b/include/linux/perf/arm_pmu.h
> index 64e1b2594025..9184f9b33740 100644
> --- a/include/linux/perf/arm_pmu.h
> +++ b/include/linux/perf/arm_pmu.h
> @@ -44,6 +44,13 @@ static_assert((PERF_EVENT_FLAG_ARCH & ARMPMU_EVT_47BIT) == ARMPMU_EVT_47BIT);
> }, \
> }
>
> +#define MAX_BRANCH_RECORDS 64
> +
> +struct branch_records {
> + struct perf_branch_stack branch_stack;
> + struct perf_branch_entry branch_entries[MAX_BRANCH_RECORDS];
> +};
> +
> /* The events for a given PMU register set. */
> struct pmu_hw_events {
> /*
> @@ -70,6 +77,8 @@ struct pmu_hw_events {
> struct arm_pmu *percpu_pmu;
>
> int irq;
> +
> + struct branch_records *branches;
> };
>
> enum armpmu_attr_groups {
> --
> 2.25.1