1 files changed, 14 insertions, 2 deletions

diff --git a/arch/powerpc/mm/40x_mmu.c b/arch/powerpc/mm/40x_mmu.c
index cecbbc76f624..29954dc28942 100644
--- a/arch/powerpc/mm/40x_mmu.c
+++ b/arch/powerpc/mm/40x_mmu.c
@@ -93,7 +93,7 @@ void __init MMU_init_hw(void)
 
 unsigned long __init mmu_mapin_ram(void)
 {
-        unsigned long v, s;
+        unsigned long v, s, mapped;
         phys_addr_t p;
 
         v = KERNELBASE;
@@ -130,5 +130,17 @@ unsigned long __init mmu_mapin_ram(void)
                 s -= LARGE_PAGE_SIZE_4M;
         }
 
-        return total_lowmem - s;
+        mapped = total_lowmem - s;
+
+        /* If the size of RAM is not an exact power of two, we may not
+         * have covered RAM in its entirety with 16 and 4 MiB
+         * pages. Consequently, restrict the top end of RAM currently
+         * allocable so that calls to the LMB to allocate PTEs for "tail"
+         * coverage with normal-sized pages (or other reasons) do not
+         * attempt to allocate outside the allowed range.
+         */
+
+        __initial_memory_limit_addr = memstart_addr + mapped;
+
+        return mapped;
 }