1 files changed, 12 insertions, 3 deletions

diff --git a/arch/ia64/mm/init.c b/arch/ia64/mm/init.c
index 65f9958db9f..1281c609ee9 100644
--- a/arch/ia64/mm/init.c
+++ b/arch/ia64/mm/init.c
@@ -382,13 +382,22 @@ ia64_mmu_init (void *my_cpu_data)
 
         if (impl_va_bits < 51 || impl_va_bits > 61)
                 panic("CPU has bogus IMPL_VA_MSB value of %lu!\n", impl_va_bits - 1);
+        /*
+         * mapped_space_bits - PAGE_SHIFT is the total number of ptes we need,
+         * which must fit into "vmlpt_bits - pte_bits" slots. Second half of
+         * the test makes sure that our mapped space doesn't overlap the
+         * unimplemented hole in the middle of the region.
+         */
+        if ((mapped_space_bits - PAGE_SHIFT > vmlpt_bits - pte_bits) ||
+            (mapped_space_bits > impl_va_bits - 1))
+                panic("Cannot build a big enough virtual-linear page table"
+                      " to cover mapped address space.\n"
+                      " Try using a smaller page size.\n");
+
 
         /* place the VMLPT at the end of each page-table mapped region: */
         pta = POW2(61) - POW2(vmlpt_bits);
 
-        if (POW2(mapped_space_bits) >= pta)
-                panic("mm/init: overlap between virtually mapped linear page table and "
-                      "mapped kernel space!");
         /*
          * Set the (virtually mapped linear) page table address.  Bit
          * 8 selects between the short and long format, bits 2-7 the