Subject: [PATCH 5/5] arm64: Document the requirement for SCR_EL3.HCE

From: Marc Zyngier <[email-masked]>
Date: Thu, 12 Aug 2021 20:02:13 +0100

It is amazing that we never documented this absolutely basic
requirement: if you boot the kernel at EL2, you'd better
enable the HVC instruction from EL3.

Really, just do it.

Signed-off-by: Marc Zyngier <[email-masked]>
---
 Documentation/arm64/booting.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/arm64/booting.rst b/Documentation/arm64/booting.rst
index a9192e7a231b..6c729d0c4bc2 100644
--- a/Documentation/arm64/booting.rst
+++ b/Documentation/arm64/booting.rst
@@ -212,6 +212,11 @@ Before jumping into the kernel, the following conditions must be met:
   - The value of SCR_EL3.FIQ must be the same as the one present at boot
     time whenever the kernel is executing.
 
+  For all systems:
+  - If EL3 is present and the kernel is entered at EL2:
+
+    - SCR_EL3.HCE (bit 8) must be initialised to 0b1.
+
   For systems with a GICv3 interrupt controller to be used in v3 mode:
   - If EL3 is present:
 
-- 
2.30.2

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