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-rw-r--r--docs/design/firmware-design.rst11
1 files changed, 10 insertions, 1 deletions
diff --git a/docs/design/firmware-design.rst b/docs/design/firmware-design.rst
index 00e199a200..dc08208262 100644
--- a/docs/design/firmware-design.rst
+++ b/docs/design/firmware-design.rst
@@ -2581,7 +2581,16 @@ Armv8.5-A
~~~~~~~~~
- Branch Target Identification feature is selected by ``BRANCH_PROTECTION``
- option set to 1. This option defaults to 0 and this is an experimental feature.
+ option set to 1. This option defaults to 0 and this is an experimental
+ feature.
+
+- Memory Tagging Extension feature is unconditionally enabled for both worlds
+ (at EL0 and S-EL0) if it is only supported at EL0. If instead it is
+ implemented at all ELs, it is unconditionally enabled for only the normal
+ world. To enable it for the secure world as well, the build option
+ ``CTX_INCLUDE_MTE_REGS`` is required. If the hardware does not implement
+ MTE support at all, it is always disabled, no matter what build options
+ are used.
Armv7-A
~~~~~~~