Reformat the pfn_info structure to ensure that

lock cmpxchg8b instructions occur only on naturally
aligned 8-byte memory values. This is needed for some
NUMA x86 systems.

Signed-off-by: Keir Fraser <keir@xensource.com>
Signed-off-by: Aravindh Puthiyaparambil <first.last@unisys.com>

3 files changed, 12 insertions, 9 deletions

diff --git a/xen/arch/x86/x86_32/mm.c b/xen/arch/x86/x86_32/mm.c
index 25c2ea7a7d..64491f02d9 100644
--- a/xen/arch/x86/x86_32/mm.c
+++ b/xen/arch/x86/x86_32/mm.c
@@ -156,6 +156,7 @@ void subarch_init_memory(struct domain *dom_xen)
      */
     if ( (offsetof(struct pfn_info, u.inuse._domain) != 
           (offsetof(struct pfn_info, count_info) + sizeof(u32))) ||
+         ((offsetof(struct pfn_info, count_info) & 7) != 0) ||
          (sizeof(struct pfn_info) != 24) )
     {
         printk("Weird pfn_info layout (%ld,%ld,%d)\n",
diff --git a/xen/arch/x86/x86_64/mm.c b/xen/arch/x86/x86_64/mm.c
index 76b3518111..a20c900fb0 100644
--- a/xen/arch/x86/x86_64/mm.c
+++ b/xen/arch/x86/x86_64/mm.c
@@ -137,8 +137,10 @@ void subarch_init_memory(struct domain *dom_xen)
      * count_info and domain fields must be adjacent, as we perform atomic
      * 64-bit operations on them.
      */
-    if ( (offsetof(struct pfn_info, u.inuse._domain) != 
-          (offsetof(struct pfn_info, count_info) + sizeof(u32))) )
+    if ( ((offsetof(struct pfn_info, u.inuse._domain) != 
+           (offsetof(struct pfn_info, count_info) + sizeof(u32)))) ||
+         ((offsetof(struct pfn_info, count_info) & 7) != 0) ||
+         (sizeof(struct pfn_info) != 40) )
     {
         printk("Weird pfn_info layout (%ld,%ld,%ld)\n",
                offsetof(struct pfn_info, count_info),
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index a68538c0a7..9b79f86d6f 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -22,9 +22,6 @@ struct pfn_info
     /* Each frame can be threaded onto a doubly-linked list. */
     struct list_head list;
 
-    /* Timestamp from 'TLB clock', used to reduce need for safety flushes. */
-    u32 tlbflush_timestamp;
-
     /* Reference count and various PGC_xxx flags and fields. */
     u32 count_info;
 
@@ -37,17 +34,20 @@ struct pfn_info
             u32 _domain; /* pickled format */
             /* Type reference count and various PGT_xxx flags and fields. */
             unsigned long type_info;
-        } inuse;
+        } __attribute__ ((packed)) inuse;
 
         /* Page is on a free list: ((count_info & PGC_count_mask) == 0). */
         struct {
+            /* Order-size of the free chunk this page is the head of. */
+            u32 order;
             /* Mask of possibly-tainted TLBs. */
             cpumask_t cpumask;
-            /* Order-size of the free chunk this page is the head of. */
-            u8 order;
-        } free;
+        } __attribute__ ((packed)) free;
 
     } u;
+
+    /* Timestamp from 'TLB clock', used to reduce need for safety flushes. */
+    u32 tlbflush_timestamp;
 };
 
  /* The following page types are MUTUALLY EXCLUSIVE. */