[xen staging] compat: add a little bit of description to xlat.lst

[patchbot@xxxxxxx]

commit fb024b779336a0f73b3aee885b2ce082e812881f
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Jul 17 17:52:14 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Jul 17 17:52:14 2020 +0200

    compat: add a little bit of description to xlat.lst
    
    Requested-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/include/xlat.lst | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/xen/include/xlat.lst b/xen/include/xlat.lst
index 0921d4a8d0..20d4dccce6 100644
--- a/xen/include/xlat.lst
+++ b/xen/include/xlat.lst
@@ -1,3 +1,22 @@
+# There are a few fundamentally different strategies for handling compat
+# (sub-)hypercalls:
+#
+# 1) Wrap a translation layer around the native hypercall. Structures involved
+# in this model should use translation (xlat) macros generated by adding
+# !-prefixed lines here.
+#
+# 2) Compile the entire hypercall function a second time, arranging for the
+# compat structures to get used in place of the native ones. There are no xlat
+# macros involved here, all that's needed are correctly translated structures.
+#
+# 3) Adhoc translation, which may or may not involve adding entries here.
+#
+# 4) Any mixture of the above.
+#
+# In all models any structures re-used in their native form should have
+# ?-mark prefixed lines added here, with the resulting checking macros invoked
+# somewhere in the code handling the hypercall or its translation.
+#
 # First column indicator:
 # ! - needs translation
 # ? - needs checking
--
generated by git-patchbot for /home/xen/git/xen.git#staging