linux-kernel - [PATCH] Revert "iommu/amd: Don't allocate with __GFP_ZERO in alloc

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Date:	Tue,  2 Jun 2015 08:45:16 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	iommu@...ts.linux-foundation.org
Cc:	linux-kernel@...r.kernel.org, Joerg Roedel <jroedel@...e.de>
Subject: [PATCH] Revert "iommu/amd: Don't allocate with __GFP_ZERO in alloc_coherent"

From: Joerg Roedel <jroedel@...e.de>

This reverts commit 5fc872c7323534e8f7dc21bab635e7a9b9659e07.

The DMA-API does not strictly require that the memory
returned by dma_alloc_coherent is zeroed out. For that
another function (dma_zalloc_coherent) should be used. But
all other x86 DMA-API implementation I checked zero out the
memory, so that some drivers rely on it and break when it is
not.

It seems the (driver-)world is not yet ready for this
change, so revert it.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 drivers/iommu/amd_iommu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index e43d489..e1c7e9e 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2930,6 +2930,7 @@ static void *alloc_coherent(struct device *dev, size_t size,
 	size	  = PAGE_ALIGN(size);
 	dma_mask  = dev->coherent_dma_mask;
 	flag     &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
+	flag     |= __GFP_ZERO;
 
 	page = alloc_pages(flag | __GFP_NOWARN,  get_order(size));
 	if (!page) {
-- 
1.8.4.5

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