[PATCH v2 1/5] x86: make dma_alloc_coherent() return zeroed memory if CMA is enabled

[Akinobu Mita <akinobu.mita@gmail.com>]

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.

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: x86@kernel.org
Cc: iommu@lists.linux-foundation.org
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
New patch from this version

 arch/x86/kernel/pci-dma.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 872079a..9644405 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -97,7 +97,6 @@ void *dma_generic_alloc_coherent(struct device *dev, size_t size,
 
 	dma_mask = dma_alloc_coherent_mask(dev, flag);
 
-	flag |= __GFP_ZERO;
 again:
 	page = NULL;
 	if (!(flag & GFP_ATOMIC))
@@ -118,7 +117,7 @@ again:
 
 		return NULL;
 	}
-
+	memset(page_address(page), 0, size);
 	*dma_addr = addr;
 	return page_address(page);
 }
-- 
1.8.3.2