[ARM] Fix some corner cases in new mm initialisation

Document that the VMALLOC_END address must be aligned to 2MB since
it must align with a PGD boundary.

Allocate the vectors page early so that the flush_cache_all() later
will cause any dirty cache lines in the direct mapping will be safely
written back.

Move the flush_cache_all() to the second local_flush_cache_tlb() and
remove the now redundant first local_flush_cache_tlb().

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 13 insertions, 11 deletions

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index c168f322ef8c..8b276ee38acf 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -420,7 +420,8 @@ static void __init bootmem_init(struct meminfo *mi)
  * Set up device the mappings.  Since we clear out the page tables for all
  * mappings above VMALLOC_END, we will remove any debug device mappings.
  * This means you have to be careful how you debug this function, or any
- * called function.  (Do it by code inspection!)
+ * called function.  This means you can't use any function or debugging
+ * method which may touch any device, otherwise the kernel _will_ crash.
  */
 static void __init devicemaps_init(struct machine_desc *mdesc)
 {
@@ -428,6 +429,12 @@ static void __init devicemaps_init(struct machine_desc *mdesc)
         unsigned long addr;
         void *vectors;
 
+        /*
+         * Allocate the vector page early.
+         */
+        vectors = alloc_bootmem_low_pages(PAGE_SIZE);
+        BUG_ON(!vectors);
+
         for (addr = VMALLOC_END; addr; addr += PGDIR_SIZE)
                 pmd_clear(pmd_off_k(addr));
 
@@ -461,12 +468,6 @@ static void __init devicemaps_init(struct machine_desc *mdesc)
         create_mapping(&map);
 #endif
 
-        flush_cache_all();
-        local_flush_tlb_all();
-
-        vectors = alloc_bootmem_low_pages(PAGE_SIZE);
-        BUG_ON(!vectors);
-
         /*
          * Create a mapping for the machine vectors at the high-vectors
          * location (0xffff0000).  If we aren't using high-vectors, also
@@ -491,12 +492,13 @@ static void __init devicemaps_init(struct machine_desc *mdesc)
                 mdesc->map_io();
 
         /*
-         * Finally flush the tlb again - this ensures that we're in a
-         * consistent state wrt the writebuffer if the writebuffer needs
-         * draining.  After this point, we can start to touch devices
-         * again.
+         * Finally flush the caches and tlb to ensure that we're in a
+         * consistent state wrt the writebuffer.  This also ensures that
+         * any write-allocated cache lines in the vector page are written
+         * back.  After this point, we can start to touch devices again.
          */
         local_flush_tlb_all();
+        flush_cache_all();
 }
 
 /*