linux-kernel - [PATCH 3.16 223/233] ARM: 8685/1: ensure memblock-limit is pmd-aligned

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Date:   Sat, 09 Sep 2017 22:47:15 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Doug Berger" <opendmb@...il.com>,
        "Mark Rutland" <mark.rutland@....com>,
        "Russell King" <rmk+kernel@...linux.org.uk>
Subject: [PATCH 3.16 223/233] ARM: 8685/1: ensure memblock-limit is
 pmd-aligned

3.16.48-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Doug Berger <opendmb@...il.com>

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.

Fixes: 965278dcb8ab ("ARM: 8356/1: mm: handle non-pmd-aligned end of RAM")
Signed-off-by: Doug Berger <opendmb@...il.com>
Suggested-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/arm/mm/mmu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1142,15 +1142,15 @@ void __init sanity_check_meminfo(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);

 	memblock_set_current_limit(memblock_limit);
 }