[POWERPC] Allow duplicate lmb_reserve() calls

At present calling lmb_reserve() (and hence lmb_add_region()) twice
for exactly the same memory region will cause strange behaviour.

This makes life difficult when booting from a flat device tree with
memory reserve map.  Which regions are automatically reserved by the
kernel has changed over time, so it's quite possible a newer kernel
could attempt to auto-reserve a region which is also explicitly listed
in the device tree's reserve map, leading to trouble.

This patch avoids the problem by making lmb_reserve() ignore a call to
reserve a previously reserved region.  It also removes a now redundant
test designed to avoid one specific case of the problem noted above.

At present, this patch deals only with duplicate reservations of an
identical region.  Attempting to reserve two different, but
overlapping regions will still cause problems.  I might post another
patch later dealing with this case, but I'm avoiding it now since it
is substantially more complicated to deal with, less likely to occur
and more likely to indicate a genuine bug elsewhere if it does occur.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 8d52b23348bd0b6cb2322fc9f87d626914268a51..15ece3abfb379cf48ca15995ace46fb0804ff3e0 100644 (file)
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -954,9 +954,6 @@ static void __init early_reserve_mem(void)
                size = *(reserve_map++);
                if (size == 0)
                        break;
-               /* skip if the reservation is for the blob */
-               if (base == self_base && size == self_size)
-                       continue;
                DBG("reserving: %llx -> %llx\n", base, size);
                lmb_reserve(base, size);
        }

diff --git a/arch/powerpc/mm/lmb.c b/arch/powerpc/mm/lmb.c
index 716a2906a24da373a9e892e1486e24f1316d271e..e3a1e8dc536a5bab3ea4c48f99e530cde5971e0b 100644 (file)
--- a/arch/powerpc/mm/lmb.c
+++ b/arch/powerpc/mm/lmb.c
@@ -146,6 +146,10 @@ static long __init lmb_add_region(struct lmb_region *rgn, unsigned long base,
                unsigned long rgnbase = rgn->region[i].base;
                unsigned long rgnsize = rgn->region[i].size;
 
+               if ((rgnbase == base) && (rgnsize == size))
+                       /* Already have this region, so we're done */
+                       return 0;
+
                adjacent = lmb_addrs_adjacent(base,size,rgnbase,rgnsize);
                if ( adjacent > 0 ) {
                        rgn->region[i].base -= size;