AArch64: Introduce RAS handling

RAS extensions are mandatory for ARMv8.2 CPUs, but are also optional
extensions to base ARMv8.0 architecture.

This patch adds build system support to enable RAS features in ARM
Trusted Firmware. A boolean build option RAS_EXTENSION is introduced for
this.

With RAS_EXTENSION, an Exception Synchronization Barrier (ESB) is
inserted at all EL3 vector entry and exit. ESBs will synchronize pending
external aborts before entering EL3, and therefore will contain and
attribute errors to lower EL execution. Any errors thus synchronized are
detected via. DISR_EL1 register.

When RAS_EXTENSION is set to 1, HANDLE_EL3_EA_FIRST must also be set to 1.

Change-Id: I38a19d84014d4d8af688bd81d61ba582c039383a
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/docs/user-guide.rst b/docs/user-guide.rst
index aed54a631..880fe7d9b 100644
--- a/docs/user-guide.rst
+++ b/docs/user-guide.rst
@@ -531,6 +531,15 @@ Common build options
    smc function id. When this option is enabled on Arm platforms, the
    option ``ARM_RECOM_STATE_ID_ENC`` needs to be set to 1 as well.
 
+-  ``RAS_EXTENSION``: When set to ``1``, enable Armv8.2 RAS features. RAS features
+   are an optional extension for pre-Armv8.2 CPUs, but are mandatory for Armv8.2
+   or later CPUs.
+
+   When ``RAS_EXTENSION`` is set to ``1``, ``HANDLE_EA_EL3_FIRST`` must also be
+   set to ``1``.
+
+   This option is disabled by default.
+
 -  ``RESET_TO_BL31``: Enable BL31 entrypoint as the CPU reset vector instead
    of the BL1 entrypoint. It can take the value 0 (CPU reset to BL1
    entrypoint) or 1 (CPU reset to BL31 entrypoint).