1Activity Monitors 2================= 3 4FEAT_AMUv1 of the Armv8-A architecture introduces the Activity Monitors 5extension. This extension describes the architecture for the Activity Monitor 6Unit (|AMU|), an optional non-invasive component for monitoring core events 7through a set of 64-bit counters. 8 9When the ``ENABLE_FEAT_AMU=1`` build option is provided, Trusted Firmware-A 10sets up the |AMU| prior to its exit from EL3, and will save and restore 11architected |AMU| counters as necessary upon suspend and resume. 12 13.. _Activity Monitor Auxiliary Counters: 14 15Auxiliary counters 16------------------ 17 18FEAT_AMUv1 describes a set of implementation-defined auxiliary counters (also 19known as group 1 counters), controlled by the ``ENABLE_AMU_AUXILIARY_COUNTERS`` 20build option. 21 22As a security precaution, Trusted Firmware-A does not enable these by default. 23Instead, platforms must configure their auxiliary counters through the 24``plat_amu_aux_enables`` platform hook. This is a per-core array indexed with 25``plat_my_core_pos()``. A core's value will be written verbatim into 26``AMCNTENSET1_EL0``. 27 28-------------- 29 30*Copyright (c) 2021-2025, Arm Limited. All rights reserved.* 31