| Activity Monitors |
| ================= |
| |
| FEAT_AMUv1 of the Armv8-A architecture introduces the Activity Monitors |
| extension. This extension describes the architecture for the Activity Monitor |
| Unit (|AMU|), an optional non-invasive component for monitoring core events |
| through a set of 64-bit counters. |
| |
| When the ``ENABLE_FEAT_AMU=1`` build option is provided, Trusted Firmware-A |
| sets up the |AMU| prior to its exit from EL3, and will save and restore |
| architected |AMU| counters as necessary upon suspend and resume. |
| |
| .. _Activity Monitor Auxiliary Counters: |
| |
| Auxiliary counters |
| ------------------ |
| |
| FEAT_AMUv1 describes a set of implementation-defined auxiliary counters (also |
| known as group 1 counters), controlled by the ``ENABLE_AMU_AUXILIARY_COUNTERS`` |
| build option. |
| |
| As a security precaution, Trusted Firmware-A does not enable these by default. |
| Instead, platforms must configure their auxiliary counters through the |
| ``plat_amu_aux_enables`` platform hook. |
| |
| -------------- |
| |
| *Copyright (c) 2021-2025, Arm Limited. All rights reserved.* |