[PATCH 2/2] x86/shadow: adjust 2-level case of SHADOW_FOREACH_L2E()

[Jan Beulich <jbeulich@xxxxxxxx>]

Coverity apparently takes issue with the assignment inside an if(), but
then only in two of the cases (sh_destroy_l2_shadow() and
sh_unhook_32b_mappings()). As it's pretty simple to break out of the
outer loop without the need for a local helper variable, adjust the code
that way.

While there, with the other "unused value" reports also in mind, further
drop a dead assignment from SHADOW_FOREACH_L1E().

Coverity-ID: 1492857
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Looking over other SHADOW_FOREACH_L<N>E() invocations wrt their uses of
"done", I find the audit ones particularly odd: The respective variables
get set only from AUDIT_FAIL() and AUDIT_FAIL_MIN(), but in both cases
after invoking BUG(), i.e. in an unreachable position.

--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -794,8 +794,7 @@ do {
                          ({ (__done = _done); }), _code);               \
     _sl1mfn = sh_next_page(_sl1mfn);                                    \
     if ( !__done )                                                      \
-        _SHADOW_FOREACH_L1E(_sl1mfn, _sl1e, _gl1p,                      \
-                             ({ (__done = _done); }), _code);           \
+        _SHADOW_FOREACH_L1E(_sl1mfn, _sl1e, _gl1p, _done, _code);       \
 } while (0)
 #else /* Everything else; l1 shadows are only one page */
 #define SHADOW_FOREACH_L1E(_sl1mfn, _sl1e, _gl1p, _done, _code)         \
@@ -808,10 +807,10 @@ do {
 /* 32-bit l2 on PAE/64: four pages, touch every second entry */
 #define SHADOW_FOREACH_L2E(_sl2mfn, _sl2e, _gl2p, _done, _dom, _code)     \
 do {                                                                      \
-    int _i, _j, __done = 0;                                               \
+    int _i, _j;                                                           \
     ASSERT(shadow_mode_external(_dom));                                   \
     ASSERT(mfn_to_page(_sl2mfn)->u.sh.type == SH_type_l2_32_shadow);      \
-    for ( _j = 0; _j < 4 && !__done; _j++ )                               \
+    for ( _j = 0; _j < 4; _j++ )                                          \
     {                                                                     \
         shadow_l2e_t *_sp = map_domain_page(_sl2mfn);                     \
         for ( _i = 0; _i < SHADOW_L2_PAGETABLE_ENTRIES; _i += 2 )         \
@@ -819,11 +818,12 @@ do {
             (_sl2e) = _sp + _i;                                           \
             if ( shadow_l2e_get_flags(*(_sl2e)) & _PAGE_PRESENT )         \
                 {_code}                                                   \
-            if ( (__done = (_done)) ) break;                              \
+            if ( _done ) break;                                           \
             increment_ptr_to_guest_entry(_gl2p);                          \
         }                                                                 \
         unmap_domain_page(_sp);                                           \
         if ( _j < 3 ) _sl2mfn = sh_next_page(_sl2mfn);                    \
+        if ( _i < SHADOW_L2_PAGETABLE_ENTRIES ) break;                    \
     }                                                                     \
 } while (0)