[xen master] docs/arm: Document Xen booting protocol on Armv8-R

[patchbot@xxxxxxx]

commit 92ad25fe3d547b622ba50226cfae8902650e1ce2
Author:     Luca Fancellu <luca.fancellu@xxxxxxx>
AuthorDate: Fri May 23 07:54:01 2025 +0100
Commit:     Michal Orzel <michal.orzel@xxxxxxx>
CommitDate: Fri May 30 08:44:15 2025 +0200

    docs/arm: Document Xen booting protocol on Armv8-R
    
    Document the requirement needed to boot Xen on Armv8-R platforms.
    
    Signed-off-by: Luca Fancellu <luca.fancellu@xxxxxxx>
    Reviewed-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
    Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
    Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 docs/misc/arm/booting.txt | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
index 21ae74837d..e9b511cae4 100644
--- a/docs/misc/arm/booting.txt
+++ b/docs/misc/arm/booting.txt
@@ -56,12 +56,17 @@ image header to determine the load address, entry point, 
etc.
 Firmware/bootloader requirements
 --------------------------------
 
-Xen relies on some settings the firmware has to configure in EL3 before 
starting Xen.
+Xen relies on some settings the firmware has to configure before starting Xen.
 
-* Xen must be entered in NS EL2 mode
+* Xen must be entered in:
+  * Non-Secure EL2 mode for Armv8-A Arm64 and Arm32, Armv8-R Arm32.
+  * Secure EL2 mode for Armv8-R Arm64.
 
-* The bit SCR_EL3.HCE (resp. SCR.HCE for 32-bit ARM) must be set to 1.
+* When EL3 is supported, the bit SCR_EL3.HCE (resp. SCR.HCE for 32-bit ARM) 
must
+  be set to 1.
 
+* Xen must be entered with MMU/MPU off and data cache disabled (SCTLR_EL2.M bit
+  and SCTLR_EL2.C set to 0). Cache state shall follow [1], [2] for MPU.
 
 [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
--
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