[Xen-devel] [PATCH v3] xen: arm: doc: Add firmware requirements

[Dirk Behme <dirk.behme@xxxxxxxxx>]

From: Dirk Behme <dirk.behme@xxxxxxxxxxxx>

Add a section about what the firmware should do in EL3 before starting Xen.

E.g guest will use HVC instruction to issue hypercall. As this can be set only
at EL3, i.e. outside Xen, document this boot requirement.

Signed-off-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
---
 docs/misc/arm/booting.txt | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/docs/misc/arm/booting.txt b/docs/misc/arm/booting.txt
index 9802e5e..c7c1d7e 100644
--- a/docs/misc/arm/booting.txt
+++ b/docs/misc/arm/booting.txt
@@ -23,6 +23,17 @@ The exceptions to this on 32-bit ARM are as follows:
 
 There are no exception on 64-bit ARM.
 
+
+Firmware/bootloader requirements
+--------------------------------
+
+Xen relies on some settings the firmware has to configure in EL3 before 
starting Xen.
+
+* Xen must be entered in NS EL2 mode
+
+* The bit SCR_EL3.HCR (resp. SCR.HCE for 32-bit ARM) must be set to 1.
+
+
 [1] linux/Documentation/arm/Booting
 Latest version: 
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm/Booting
 
-- 
2.8.1


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