streamline guest copy operations

- use the variants not validating the VA range when writing back
  structures/fields to the same space that they were previously read
  from
- when only a single field of a structure actually changed, copy back
  just that field where possible
- consolidate copying back results in a few places

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index 35653b7d64..d2f2125181 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -1074,7 +1074,7 @@ long subarch_memory_op(int op, XEN_GUEST_HANDLE_PARAM(void) arg)
         }
 
         xmml.nr_extents = i;
-        if ( copy_to_guest(arg, &xmml, 1) )
+        if ( __copy_to_guest(arg, &xmml, 1) )
             return -EFAULT;
 
         break;
@@ -1092,7 +1092,7 @@ long subarch_memory_op(int op, XEN_GUEST_HANDLE_PARAM(void) arg)
         if ( copy_from_guest(&meo, arg, 1) )
             return -EFAULT;
         rc = do_mem_event_op(op, meo.domain, (void *) &meo);
-        if ( !rc && copy_to_guest(arg, &meo, 1) )
+        if ( !rc && __copy_to_guest(arg, &meo, 1) )
             return -EFAULT;
         break;
     }
@@ -1104,7 +1104,7 @@ long subarch_memory_op(int op, XEN_GUEST_HANDLE_PARAM(void) arg)
         if ( mso.op == XENMEM_sharing_op_audit )
             return mem_sharing_audit(); 
         rc = do_mem_event_op(op, mso.domain, (void *) &mso);
-        if ( !rc && copy_to_guest(arg, &mso, 1) )
+        if ( !rc && __copy_to_guest(arg, &mso, 1) )
             return -EFAULT;
         break;
     }