On 29/04/2025 16:20, Luca Fancellu wrote:
Document the requirement needed to boot Xen on Armv8-R platforms.
Signed-off-by: Luca Fancellu <luca.fance...@arm.com>
---
v4 changes:
- New patch
---
docs/misc/arm/booting.txt | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
index 21ae74837dcc..719af74f1e69 100644
--- a/docs/misc/arm/booting.txt
+++ b/docs/misc/arm/booting.txt
@@ -62,6 +62,14 @@ Xen relies on some settings the firmware has to configure in
EL3 before starting
* The bit SCR_EL3.HCE (resp. SCR.HCE for 32-bit ARM) must be set to 1.
+When Xen runs on Armv8-R, the highest exception level is EL2 and the only
+available state is secure (S) on Arm64 and non secure (NS) on Arm32, hence the
+above requirements need to be adjusted to this case:
> +> +* Xen must be entered in S EL2 mode on Arm64 and in NS EL2 mode
on Arm32.
I think it would be better to update the line "Xen must be entered in NS
EL2 mode" to clarify the state for 64-bit Arm.
> +> +* Xen must be entered with MPU off and data cache disabled
(SCTLR_EL2.M bit and
+ SCTLR_EL2.C set to 0).
This line is valid for Armv8-A/Armv7-A when using the Image/zImage protocol.
[1] linux/Documentation/arm/booting.rst
Latest version:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/arch/arm/booting.rst
--
Julien Grall
