[Xen-devel] [PATCH v3] docs/arm64: update the documention for loading XSM support

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Julien Grall writes ("Re: [PATCH v2] docs/arm64: update the documention for 
loading XSM support"):
> The new version looks good to me:
> Acked-by: Julien Grall <julien.grall@xxxxxxx>
> 
> Can a native speaker (Ian, Konrad, George) double-check the wording)?

I found it rather difficult to read.  See updated version, attached.

I dropped your ack because I want to be sure that the new version
still describes the actual behaviour.  I kept Wei's release-ack.

Thanks,
Ian.

From bd8f24667d353a4c90203d51c1fdb42a66b79973 Mon Sep 17 00:00:00 2001
From: Fu Wei <fu.wei@xxxxxxxxxx>
Date: Thu, 21 Apr 2016 19:07:09 +0800
Subject: [PATCH] docs/arm64: update the documention for loading XSM support

This patch updates the documentation for allowing detection of an XSM
module that lacks a specific compatible string.

(This mechanism was added in commit ca32012341f3,
 "xen/arm64: check XSM Magic from the second unknown module.")

Signed-off-by: Fu Wei <fu.wei@xxxxxxxxxx>
Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 docs/misc/arm/device-tree/booting.txt |   27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/docs/misc/arm/device-tree/booting.txt 
b/docs/misc/arm/device-tree/booting.txt
index ad98bf3..f3179d6 100644
--- a/docs/misc/arm/device-tree/booting.txt
+++ b/docs/misc/arm/device-tree/booting.txt
@@ -24,10 +24,29 @@ Each node contains the following properties:
        string (which must always be present).
 
        Xen will assume that the first module which lacks a more
-       specific compatible string is a "multiboot,kernel" and that
-       the second such is a "multiboot,ramdisk". Any subsequent
-       modules which lack a specific compatiblity string will not
-       receive any special treatment.
+       specific compatible string is a "multiboot,kernel".
+
+       Xen will examine each module, starting from the second
+       module that lacks a specific compatible string.  Xen will
+        check each such module for the XSM Magic number:
+
+       - For a module which has the XSM Magic number: it will be
+          treated by Xen as if its compatible string was
+          "xen,xsm-policy";
+
+       - For a module which does not have the XSM Magic: the second
+          module lacking a compatible string will be treated by Xen as
+          if its compatible string was "multiboot,ramdisk"; for the
+          third and subsequent modules which lack a specific
+          compatible string, Xen will not apply any special treatment.
+
+       This means if the ramdisk module is present and does not have the
+       compatible string "multiboot,ramdisk", then it must always be the
+       second module.
+
+       Note: This XSM Magic detection behavior was introduced by Xen 4.7.
+       Xen 4.6 (and downwards) still requires the XSM module to have the
+       compatible string "xen,xsm-policy".
 
        Xen 4.4 supported a different set of legacy compatible strings
        which remain supported such that systems supporting both 4.4
-- 
1.7.10.4


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