arm64: mops: document boot requirements for MOPS

FEAT_MOPS introduces new instructions, we require that these
instructions not execute as UNDEFINED when we identify that the feature
is supported.

Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Link: https://lore.kernel.org/r/20230509142235.3284028-5-kristina.martsenko@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/Documentation/arm64/booting.rst b/Documentation/arm64/booting.rst
index ffeccdd6bdac94420d2839c6f1966faa6d253fd3..b3bbf330ed0abdf15871c4a627e1b2b399e36cc9 100644 (file)
--- a/Documentation/arm64/booting.rst
+++ b/Documentation/arm64/booting.rst
@@ -379,6 +379,12 @@ Before jumping into the kernel, the following conditions must be met:
 
     - SMCR_EL2.EZT0 (bit 30) must be initialised to 0b1.
 
+  For CPUs with Memory Copy and Memory Set instructions (FEAT_MOPS):
+
+  - If the kernel is entered at EL1 and EL2 is present:
+
+    - HCRX_EL2.MSCEn (bit 11) must be initialised to 0b1.
+
 The requirements described above for CPU mode, caches, MMUs, architected
 timers, coherency and system registers apply to all CPUs.  All CPUs must
 enter the kernel in the same exception level.  Where the values documented