The patch titled
Subject: ARM: CMA: avoid double mapping to the CMA area if CONFIG_HIGHMEM=y
has been added to the -mm tree. Its filename is
arm-cma-avoid-double-mapping-to-the-cma-area-if-config_highmem-=-y.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/arm-cma-avoid-double-mapping-to-the-cma-area-if-config_highmem-%3D-y.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/arm-cma-avoid-double-mapping-to-the-cma-area-if-config_highmem-%3D-y.patch
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From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Subject: ARM: CMA: avoid double mapping to the CMA area if CONFIG_HIGHMEM=y
CMA area is now managed by the separate zone, ZONE_MOVABLE, to fix many MM
related problems. In this implementation, if CONFIG_HIGHMEM = y, then
ZONE_MOVABLE is considered as HIGHMEM and the memory of the CMA area is
also considered as HIGHMEM. That means that they are considered as the
page without direct mapping. However, CMA area could be in a lowmem and
the memory could have direct mapping.
In ARM, when establishing a new mapping for DMA, direct mapping should be
cleared since two mapping with different cache policy could cause unknown
problem. With this patch, PageHighmem() for the CMA memory located in
lowmem returns true so that the function for DMA mapping cannot notice
whether it needs to clear direct mapping or not, correctly. To handle
this situation, this patch always clears direct mapping for such CMA
memory.
Link: http://lkml.kernel.org/r/1503556593-10720-4-git-send-email-iamjoonsoo.kim@xxxxxxx
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Laura Abbott <lauraa@xxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Michal Nazarewicz <mina86@xxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/arm/mm/dma-mapping.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff -puN arch/arm/mm/dma-mapping.c~arm-cma-avoid-double-mapping-to-the-cma-area-if-config_highmem-=-y arch/arm/mm/dma-mapping.c
--- a/arch/arm/mm/dma-mapping.c~arm-cma-avoid-double-mapping-to-the-cma-area-if-config_highmem-=-y
+++ a/arch/arm/mm/dma-mapping.c
@@ -513,7 +513,13 @@ void __init dma_contiguous_remap(void)
flush_tlb_kernel_range(__phys_to_virt(start),
__phys_to_virt(end));
- iotable_init(&map, 1);
+ /*
+ * For highmem system, all the memory in CMA region will be
+ * considered as highmem even if it's physical address belong
+ * to lowmem. Therefore, re-mapping isn't required.
+ */
+ if (!IS_ENABLED(CONFIG_HIGHMEM))
+ iotable_init(&map, 1);
}
}
_
Patches currently in -mm which might be from iamjoonsoo.kim@xxxxxxx are
mm-mlock-use-page_zone-instead-of-page_zone_id.patch
mm-cma-manage-the-memory-of-the-cma-area-by-using-the-zone_movable.patch
mm-cma-remove-alloc_cma.patch
arm-cma-avoid-double-mapping-to-the-cma-area-if-config_highmem-=-y.patch
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