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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>
This commit is contained in:
Akinobu Mita 2014-06-04 16:06:48 -07:00 committed by Linus Torvalds
parent 6b4ebc3a90
commit d92ef66c4f
1 changed files with 2 additions and 2 deletions
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4
arch/x86/kernel/pci-dma.c
View File

@ -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);
}