diff options
author | Akinobu Mita <akinobu.mita@gmail.com> | 2014-06-04 16:06:48 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-06-04 16:53:57 -0700 |
commit | d92ef66c4f8fdf7a24736b1ab6c48d32de9bfc07 (patch) | |
tree | bde652bc3ad56f3496fc3fe980c6b9dc6600efb5 /arch/x86/kernel/pci-dma.c | |
parent | 6b4ebc3a9078c5b7b8c4cf495a0b1d2d0e0bfe7a (diff) |
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@gmail.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Don Dutile <ddutile@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86/kernel/pci-dma.c')
-rw-r--r-- | arch/x86/kernel/pci-dma.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c index f7d0672481fd..e5f4e9629e61 100644 --- a/arch/x86/kernel/pci-dma.c +++ b/arch/x86/kernel/pci-dma.c @@ -97,7 +97,7 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size, dma_mask = dma_alloc_coherent_mask(dev, flag); - flag |= __GFP_ZERO; + flag &= ~__GFP_ZERO; again: page = NULL; /* CMA can be used only in the context which permits sleeping */ @@ -120,7 +120,7 @@ again: return NULL; } - + memset(page_address(page), 0, size); *dma_addr = addr; return page_address(page); } |