[XenPPC] [RFC] fix stupid grant table flags

[Hollis Blanchard <hollisb@xxxxxxxxxx>]

The final issue before our upstream merge is sorting out the cmpxchg on
struct grant_entry->flags, which is a 16-bit quantity (and our atomic
instructions only operate on 4/8 byte quanities).

Since it's part of a larger structure, it's safe to do the larger store,
so these patches, just like the evtchn_upcall_pending patch, should
work. I think the structure alignment will also work out...?

diff -r ab08d443113d xen/common/grant_table.c
--- a/xen/common/grant_table.c  Wed Jun 21 13:36:49 2006 -0500
+++ b/xen/common/grant_table.c  Wed Jun 21 13:42:23 2006 -0500
@@ -287,10 +287,10 @@ __gnttab_map_grant_ref(
 
     if ( !(op->flags & GNTMAP_readonly) &&
          !(act->pin & (GNTPIN_hstw_mask|GNTPIN_devw_mask)) )
-        clear_bit(_GTF_writing, &sha->flags);
+        clear_entry_flag(_GTF_writing, &sha->flags);
 
     if ( !act->pin )
-        clear_bit(_GTF_reading, &sha->flags);
+        clear_entry_flag(_GTF_reading, &sha->flags);
 
  unlock_out:
     spin_unlock(&rd->grant_table->lock);
@@ -425,10 +425,10 @@ __gnttab_unmap_grant_ref(
 
     if ( ((act->pin & (GNTPIN_devw_mask|GNTPIN_hstw_mask)) == 0) &&
          !(flags & GNTMAP_readonly) )
-        clear_bit(_GTF_writing, &sha->flags);
+        clear_entry_flag(_GTF_writing, &sha->flags);
 
     if ( act->pin == 0 )
-        clear_bit(_GTF_reading, &sha->flags);
+        clear_entry_flag(_GTF_reading, &sha->flags);
 
  unmap_out:
     op->status = rc;
@@ -889,11 +889,11 @@ gnttab_release_mappings(
             }
 
             if ( (act->pin & (GNTPIN_devw_mask|GNTPIN_hstw_mask)) == 0 )
-                clear_bit(_GTF_writing, &sha->flags);
+                clear_entry_flag(_GTF_writing, &sha->flags);
         }
 
         if ( act->pin == 0 )
-            clear_bit(_GTF_reading, &sha->flags);
+            clear_entry_flag(_GTF_reading, &sha->flags);
 
         spin_unlock(&rd->grant_table->lock);
 
diff -r ab08d443113d xen/include/asm-ppc/grant_table.h
--- a/xen/include/asm-ppc/grant_table.h Wed Jun 21 13:36:49 2006 -0500
+++ b/xen/include/asm-ppc/grant_table.h Wed Jun 21 13:42:23 2006 -0500
@@ -6,4 +6,6 @@
 #define mark_dirty(d, f) ((void )0)
 #include "../asm-x86/grant_table.h"
 
+#define clear_entry_flag(nr, flags) clear_bit((nr), (int *)(flags));
+
 #endif  /* __ASM_PPC_GRANT_TABLE_H__ */
diff -r ab08d443113d xen/include/public/grant_table.h
--- a/xen/include/public/grant_table.h  Wed Jun 21 13:36:49 2006 -0500
+++ b/xen/include/public/grant_table.h  Wed Jun 21 13:42:23 2006 -0500
@@ -73,11 +73,7 @@
  */
 struct grant_entry {
     /* GTF_xxx: various type and flag information.  [XEN,GST] */
-#if defined(__powerpc__)
-    ulong flags;
-#else
     uint16_t flags;
-#endif
     /* The domain being granted foreign privileges. [GST] */
     domid_t  domid;
     /*



And the Linux patch:

diff -r 6f3d44537b76 drivers/xen/core/gnttab.c
--- a/drivers/xen/core/gnttab.c Fri Jun 16 16:07:38 2006 -0500
+++ b/drivers/xen/core/gnttab.c Wed Jun 21 13:42:56 2006 -0500
@@ -201,7 +201,7 @@ gnttab_end_foreign_access_ref(grant_ref_
                        printk(KERN_ALERT "WARNING: g.e. still in use!\n");
                        return 0;
                }
-       } while ((nflags = synch_cmpxchg(&shared[ref].flags, flags, 0)) !=
+       } while ((nflags = gnttab_cmpxchg_flags(&shared[ref].flags, flags, 0)) 
!=
                 flags);
 
        return 1;
@@ -256,7 +256,7 @@ gnttab_end_foreign_transfer_ref(grant_re
          * reference and return failure (== 0).
          */
        while (!((flags = shared[ref].flags) & GTF_transfer_committed)) {
-               if (synch_cmpxchg(&shared[ref].flags, flags, 0) == flags)
+               if (gnttab_cmpxchg_flags(&shared[ref].flags, flags, 0) == flags)
                        return 0;
                cpu_relax();
        }
diff -r 6f3d44537b76 include/asm-powerpc/xen/asm/synch_bitops.h
--- a/include/asm-powerpc/xen/asm/synch_bitops.h        Fri Jun 16 16:07:38 
2006 -0500
+++ b/include/asm-powerpc/xen/asm/synch_bitops.h        Wed Jun 21 13:42:56 
2006 -0500
@@ -6,6 +6,8 @@
 
 #ifdef CONFIG_SMP
 #include <asm/bitops.h>
+
+#define gnttab_cmpxchg_flags(ptr,o,n) synch_cmpxchg((int *)(ptr),o,n)
 
 #define synch_change_bit(a,b) change_bit(a,b)
 #define synch_clear_bit(a,b) clear_bit(a,b)
diff -r 6f3d44537b76 include/xen/interface/grant_table.h
--- a/include/xen/interface/grant_table.h       Fri Jun 16 16:07:38 2006 -0500
+++ b/include/xen/interface/grant_table.h       Wed Jun 21 13:42:56 2006 -0500
@@ -73,11 +73,7 @@
  */
 struct grant_entry {
     /* GTF_xxx: various type and flag information.  [XEN,GST] */
-#if defined(__powerpc__)
-    ulong flags;
-#else
     uint16_t flags;
-#endif
     /* The domain being granted foreign privileges. [GST] */
     domid_t  domid;
     /*


-- 
Hollis Blanchard
IBM Linux Technology Center


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