[PATCH] xen/public: partially revert commit 7c7f7e8fba01

[Juergen Gross <jgross@xxxxxxxx>]

Commit 7c7f7e8fba01 changed xen/include/public/memory.h in an incompatible
way. Unfortunately the changed parts were already in use in the Linux
kernel, so an update of the header in the kernel would result in a build
breakage.

Even when removing its usage from the kernel the used flag bit should be
marked as reserved in order to avoid to give it a different semantic in
the future.

Do a partial revert of said commit in order to enable the kernel to take
an updated version of memory.h.

Fixes: 7c7f7e8fba01 ("include/public/memory.h: remove the 
XENMEM_rsrc_acq_caller_owned flag")
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/common/memory.c         |  2 +-
 xen/include/public/memory.h | 12 +++++++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/xen/common/memory.c b/xen/common/memory.c
index 0d7c413df8..9b5214a8a9 100644
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -1234,7 +1234,7 @@ static int acquire_resource(
     if ( copy_from_guest(&xmar, arg, 1) )
         return -EFAULT;
 
-    if ( xmar.pad != 0 )
+    if ( xmar.flags != 0 )
         return -EINVAL;
 
     /*
diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index 383a9468c3..fd768e0b7b 100644
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -662,7 +662,17 @@ struct xen_mem_acquire_resource {
      * two calls.
      */
     uint32_t nr_frames;
-    uint32_t pad;
+
+    /*
+     * OUT - Must be zero on entry. On return this may contain a bitwise
+     *       OR of the following values.
+     */
+    uint32_t flags;
+
+    /* No longer supported - will be never set */
+#define _XENMEM_rsrc_acq_caller_owned 0
+#define XENMEM_rsrc_acq_caller_owned (1u << _XENMEM_rsrc_acq_caller_owned)
+
     /*
      * IN - the index of the initial frame to be mapped. This parameter
      *      is ignored if nr_frames is 0.  This value may be updated
-- 
2.34.1