Hi Jan,
On 29/04/2021 14:10, Jan Beulich wrote:
With there being a way to disable v2 support, telling new guests to use
v2 exclusively is not a good suggestion.
Signed-off-by: Jan Beulich <[email protected]>
--- a/xen/include/public/grant_table.h
+++ b/xen/include/public/grant_table.h
@@ -121,8 +121,10 @@ typedef uint32_t grant_ref_t;
*/
/*
- * Version 1 of the grant table entry structure is maintained purely
- * for backwards compatibility. New guests should use version 2.
+ * Version 1 of the grant table entry structure is maintained largely for
+ * backwards compatibility. New guests are recommended to support using
+ * version 2 to overcome version 1 limitations, but to be able to fall back
+ * to version 1.
v2 is not supported on Arm and I don't see it coming anytime soon.
AFAIK, Linux will also not use grant table v2 unless the guest has a
address space larger than 44 (?) bits.
I can't remember why Linux decided to not use it everywhere, but this is
a sign that v2 is not always desired.
So I think it would be better to recommend new guest to use v1 unless
they hit the limitations (to be details).
Cheers,
--
Julien Grall
