This patch establishes a new abstraction of sharing handles (encoded as a 64bit

int), each corresponding to a single sharable pages. Externally all sharing related
operations (e.g. nominate/share) will use sharing handles, thus solving a lot of
consistency problems (like: is this sharable page still the same sharable page
as before).
Internally, sharing handles can be translated to the MFNs (using a newly created
hashtable), and then for each MFNs a doubly linked list of GFNs translating to
this MFN is maintained. Finally, sharing handle is stored in page_info strucutre
for each sharable MFN.
All this allows to share and unshare pages efficiently. However, at the moment a
single lock is used to protect the sharing handle hash table. For scalability
reasons, the locking needs to be made more granular.

Signed-off-by: Grzegorz Milos <Grzegorz.Milos@citrix.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index 5c3ab88c3a..5f8aeb5d00 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -43,6 +43,8 @@ struct page_info
         struct page_list_entry list;
         /* For non-pinnable shadows, a higher entry that points at us. */
         paddr_t up;
+        /* For shared/sharable pages the sharing handle */
+        uint64_t shr_handle; 
     };
 
     /* Reference count and various PGC_xxx flags and fields. */