ARM: 8685/1: ensure memblock-limit is pmd-aligned

The pmd containing memblock_limit is cleared by prepare_page_table()
which creates the opportunity for early_alloc() to allocate unmapped
memory if memblock_limit is not pmd aligned causing a boot-time hang.

Commit 965278dcb8ab ("ARM: 8356/1: mm: handle non-pmd-aligned end of RAM")
attempted to resolve this problem, but there is a path through the
adjust_lowmem_bounds() routine where if all memory regions start and
end on pmd-aligned addresses the memblock_limit will be set to
arm_lowmem_limit.

Since arm_lowmem_limit can be affected by the vmalloc early parameter,
the value of arm_lowmem_limit may not be pmd-aligned. This commit
corrects this oversight such that memblock_limit is always rounded
down to pmd-alignment.

Fixes: 965278dcb8ab ("ARM: 8356/1: mm: handle non-pmd-aligned end of RAM")
Signed-off-by: Doug Berger <opendmb@gmail.com>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 4 insertions, 4 deletions

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 31af3cb59a60..e46a6a446cdd 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1218,15 +1218,15 @@ void __init adjust_lowmem_bounds(void)
 
         high_memory = __va(arm_lowmem_limit - 1) + 1;
 
+        if (!memblock_limit)
+                memblock_limit = arm_lowmem_limit;
+
         /*
          * Round the memblock limit down to a pmd size.  This
          * helps to ensure that we will allocate memory from the
          * last full pmd, which should be mapped.
          */
-        if (memblock_limit)
-                memblock_limit = round_down(memblock_limit, PMD_SIZE);
-        if (!memblock_limit)
-                memblock_limit = arm_lowmem_limit;
+        memblock_limit = round_down(memblock_limit, PMD_SIZE);
 
         if (!IS_ENABLED(CONFIG_HIGHMEM) || cache_is_vipt_aliasing()) {
                 if (memblock_end_of_DRAM() > arm_lowmem_limit) {