x86/mm/shadow: remove dead code for avoiding Xen entries on 32-bit tables.

All non-external-mode (==PV) guests have 4-level pagetables now that
the PAE build of Xen is gone.

This patch should have no effect, since the condition it removes could
never be true anyway: the l2 offset of HYPERVISOR_VIRT_START on 64-bit
Xen is much higher than any l2 offset we could have seen in the
tables (and indeed bigger than the 'int' type, which clang was
complaining about).  Actual compat PV guest xen entries are handled by
the equivalent test in the 64-bit SHADOW_FOREACH_L2E() below.

Reported-by: Julien Grall <julien.grall@linaro.org>
Signed-off-by: Tim Deegan <tim@xen.org>

diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index a8ef75eb14bda45c3adb91ed9503cd802fc34ef7..e2160636ba15e54f21a803010f728282e24f4478 100644 (file)
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -1305,26 +1305,23 @@ do {                                                                    \
 
 #if GUEST_PAGING_LEVELS == 2
 
-/* 32-bit l2 on PAE/64: four pages, touch every second entry, and avoid Xen */
+/* 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 _xen = !shadow_mode_external(_dom);                               \
-    ASSERT(mfn_to_page(_sl2mfn)->u.sh.type == SH_type_l2_32_shadow);\
+    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++ )                               \
     {                                                                     \
         shadow_l2e_t *_sp = sh_map_domain_page(_sl2mfn);                  \
         for ( _i = 0; _i < SHADOW_L2_PAGETABLE_ENTRIES; _i += 2 )         \
-            if ( (!(_xen))                                                \
-                 || ((_j * SHADOW_L2_PAGETABLE_ENTRIES) + _i)             \
-                 < (HYPERVISOR_VIRT_START >> SHADOW_L2_PAGETABLE_SHIFT) ) \
-            {                                                             \
-                (_sl2e) = _sp + _i;                                       \
-                if ( shadow_l2e_get_flags(*(_sl2e)) & _PAGE_PRESENT )     \
-                    {_code}                                               \
-                if ( (__done = (_done)) ) break;                          \
-                increment_ptr_to_guest_entry(_gl2p);                      \
-            }                                                             \
+        {                                                                 \
+            (_sl2e) = _sp + _i;                                           \
+            if ( shadow_l2e_get_flags(*(_sl2e)) & _PAGE_PRESENT )         \
+                {_code}                                                   \
+            if ( (__done = (_done)) ) break;                              \
+            increment_ptr_to_guest_entry(_gl2p);                          \
+        }                                                                 \
         sh_unmap_domain_page(_sp);                                        \
         if ( _j < 3 ) _sl2mfn = sh_next_page(_sl2mfn);                    \
     }                                                                     \
@@ -1332,26 +1329,22 @@ do {                                                                      \
 
 #elif GUEST_PAGING_LEVELS == 3
 
-/* PAE: if it's an l2h, don't touch Xen mappings */
+/* PAE: touch all entries */
 #define SHADOW_FOREACH_L2E(_sl2mfn, _sl2e, _gl2p, _done, _dom, _code)      \
 do {                                                                       \
     int _i;                                                                \
-    int _xen = !shadow_mode_external(_dom);                                \
     shadow_l2e_t *_sp = sh_map_domain_page((_sl2mfn));                     \
-    ASSERT(mfn_to_page(_sl2mfn)->u.sh.type == SH_type_l2_pae_shadow \
-           || mfn_to_page(_sl2mfn)->u.sh.type == SH_type_l2h_pae_shadow);\
+    ASSERT(shadow_mode_external(_dom));                                    \
+    ASSERT(mfn_to_page(_sl2mfn)->u.sh.type == SH_type_l2_pae_shadow        \
+           || mfn_to_page(_sl2mfn)->u.sh.type == SH_type_l2h_pae_shadow);  \
     for ( _i = 0; _i < SHADOW_L2_PAGETABLE_ENTRIES; _i++ )                 \
-        if ( (!(_xen))                                                     \
-             || mfn_to_page(_sl2mfn)->u.sh.type != SH_type_l2h_pae_shadow\
-             || ((_i + (3 * SHADOW_L2_PAGETABLE_ENTRIES))                  \
-                 < (HYPERVISOR_VIRT_START >> SHADOW_L2_PAGETABLE_SHIFT)) ) \
-        {                                                                  \
-            (_sl2e) = _sp + _i;                                            \
-            if ( shadow_l2e_get_flags(*(_sl2e)) & _PAGE_PRESENT )          \
-                {_code}                                                    \
-            if ( _done ) break;                                            \
-            increment_ptr_to_guest_entry(_gl2p);                           \
-        }                                                                  \
+    {                                                                      \
+        (_sl2e) = _sp + _i;                                                \
+        if ( shadow_l2e_get_flags(*(_sl2e)) & _PAGE_PRESENT )              \
+            {_code}                                                        \
+        if ( _done ) break;                                                \
+        increment_ptr_to_guest_entry(_gl2p);                               \
+    }                                                                      \
     sh_unmap_domain_page(_sp);                                             \
 } while (0)