Subject: + x86-make-dma_alloc_coherent-return-zeroed-memory-if-cma-is-enabled.patch added to -mm tree
To: akinobu.mita@xxxxxxxxx,andi@xxxxxxxxxxxxxx,ddutile@xxxxxxxxxx,dwmw2@xxxxxxxxxxxxx,hpa@xxxxxxxxx,konrad.wilk@xxxxxxxxxx,m.szyprowski@xxxxxxxxxxx,mingo@xxxxxxxxxx,tglx@xxxxxxxxxxxxx,yinghai@xxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 16 Apr 2014 12:44:44 -0700
The patch titled
Subject: x86: make dma_alloc_coherent() return zeroed memory if CMA is enabled
has been added to the -mm tree. Its filename is
x86-make-dma_alloc_coherent-return-zeroed-memory-if-cma-is-enabled.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/x86-make-dma_alloc_coherent-return-zeroed-memory-if-cma-is-enabled.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/x86-make-dma_alloc_coherent-return-zeroed-memory-if-cma-is-enabled.patch
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From: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Subject: x86: make dma_alloc_coherent() return zeroed memory if CMA is enabled
This patchset enhances the DMA Contiguous Memory Allocator on x86.
Currently the DMA CMA is only supported with pci-nommu dma_map_ops and
furthermore it can't be enabled on x86_64. But I would like to allocate
big contiguous memory with dma_alloc_coherent() and tell it to the device
that requires it, regardless of which dma mapping implementation is
actually used in the system.
So this makes it work with swiotlb and intel-iommu dma_map_ops, too. And
this also extends "cma=" kernel parameter to specify placement constraint
by the physical address range of memory allocations. For example, CMA
allocates memory below 4GB by "cma=64M@0-4G", it is required for the
devices only supporting 32-bit addressing on 64-bit systems without iommu.
This patch (of 5):
Calling dma_alloc_coherent() with __GFP_ZERO must return zeroed memory.
But when the contiguous memory allocator (CMA) is enabled on x86 and the
memory region is allocated by dma_alloc_from_contiguous(), it doesn't
return zeroed memory. Because dma_generic_alloc_coherent() forgot to fill
the memory region with zero if it was allocated by
dma_alloc_from_contiguous()
Most implementations of dma_alloc_coherent() return zeroed memory
regardless of whether __GFP_ZERO is specified. So this fixes it by
unconditionally zeroing the allocated memory region.
Alternatively, we could fix dma_alloc_from_contiguous() to return zeroed
out memory and remove memset() from all caller of it. But we can't simply
remove the memset on arm because __dma_clear_buffer() is used there for
ensuring cache flushing and it is used in many places. Of course we can
do redundant memset in dma_alloc_from_contiguous(), but I think this patch
is less impact for fixing this problem.
Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Don Dutile <ddutile@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/pci-dma.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff -puN arch/x86/kernel/pci-dma.c~x86-make-dma_alloc_coherent-return-zeroed-memory-if-cma-is-enabled arch/x86/kernel/pci-dma.c
--- a/arch/x86/kernel/pci-dma.c~x86-make-dma_alloc_coherent-return-zeroed-memory-if-cma-is-enabled
+++ a/arch/x86/kernel/pci-dma.c
@@ -97,7 +97,6 @@ void *dma_generic_alloc_coherent(struct
dma_mask = dma_alloc_coherent_mask(dev, flag);
- flag |= __GFP_ZERO;
again:
page = NULL;
/* CMA can be used only in the context which permits sleeping */
@@ -120,7 +119,7 @@ again:
return NULL;
}
-
+ memset(page_address(page), 0, size);
*dma_addr = addr;
return page_address(page);
}
_
Patches currently in -mm which might be from akinobu.mita@xxxxxxxxx are
x86-make-dma_alloc_coherent-return-zeroed-memory-if-cma-is-enabled.patch
x86-enable-dma-cma-with-swiotlb.patch
intel-iommu-integrate-dma-cma.patch
memblock-introduce-memblock_alloc_range.patch
cma-add-placement-specifier-for-cma=-kernel-parameter.patch
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