fix(amu): fault handling on EL2 context switch

The HAFGRTR_EL2 register is UNDEFINED unless the CPU supports both
FEAT_FGT and FEAT_AMUv1. FEAT_FGT is mandatory for v8.6-A and upwards,
but FEAT_AMUv1 is optional (from v8.4-A upwards), and as such any
8.6-A cores today without support for FEAT_AMUv1 will trigger an
undefined instruction exception on accessing this register.

Currently ARM_ARCH_AT_LEAST macro has been used to associate with an
architecture extension allowing to access HAFGRTR_EL2 register. This
condition should be replaced with macros specific to individual
features. This patch adds a new set of macros "ENABLE_FEAT_FGT,
ENABLE_FEAT_AMUv1, ENABLE_FEAT_ECV" under build options to provide
controlled access to the HAFGRTR_EL2 register.

Further to ensure that the the build options passed comply
with the given hardware implementation, a feature detection mechanism,
checking whether build options match with the architecture is required
at bootime. This will be implemented and pushed later in a separate

Signed-off-by: Jayanth Dodderi Chidanand <>
Change-Id: Ie390f4babe233b8b09455290277edbddecd33ead
4 files changed