Patch "ARM: 8685/1: ensure memblock-limit is pmd-aligned" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

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

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     arm-8685-1-ensure-memblock-limit-is-pmd-aligned.patch

and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Doug Berger <[email protected]>
Date: Thu, 29 Jun 2017 18:41:36 +0100
Subject: ARM: 8685/1: ensure memblock-limit is pmd-aligned

From: Doug Berger <[email protected]>

commit 9e25ebfe56ece7541cd10a20d715cbdd148a2e06 upstream.

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.

---
 arch/arm/mm/mmu.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

@@ -1211,15 +1211,15 @@ 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) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/arm-8685-1-ensure-memblock-limit-is-pmd-aligned.patch