From d92ef66c4f8fdf7a24736b1ab6c48d32de9bfc07 Mon Sep 17 00:00:00 2001 From: Akinobu Mita Date: Wed, 4 Jun 2014 16:06:48 -0700 Subject: [PATCH] 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 Cc: Marek Szyprowski Cc: Konrad Rzeszutek Wilk Cc: David Woodhouse Cc: Don Dutile Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Andi Kleen Cc: Yinghai Lu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/x86/kernel/pci-dma.c | 4 ++-- 1 file 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); } -- 2.20.1