linux-kernel - [PATCH]: PCI: GART iommu alignment fixes

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Date:	Mon, 21 Jul 2008 10:15:27 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Cc:	Prarit Bhargava <prarit@...hat.com>
Subject: [PATCH]: PCI: GART iommu alignment fixes

pci_alloc_consistent/dma_alloc_coherent is supposed to return size aligned
addresses.

>From Documentation/DMA-mapping.txt:

"pci_alloc_consistent returns two values: the virtual address which you
can use to access it from the CPU and dma_handle which you pass to the
card.

The cpu return address and the DMA bus master address are both
guaranteed to be aligned to the smallest PAGE_SIZE order which
is greater than or equal to the requested size.  This invariant
exists (for example) to guarantee that if you allocate a chunk
which is smaller than or equal to 64 kilobytes, the extent of the
buffer you receive will not cross a 64K boundary."

Fix the GART's alloc_iommu code to return a size aligned address.  Also fix
an incorrect alignment calculation in the iommu-helper code.

Signed-off-by: Prarit Bhargava <prarit@...hat.com>

diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
index faf3229..329718e 100644
--- a/arch/x86/kernel/pci-gart_64.c
+++ b/arch/x86/kernel/pci-gart_64.c
@@ -96,11 +96,12 @@ static unsigned long alloc_iommu(struct device *dev, int size)

 	spin_lock_irqsave(&iommu_bitmap_lock, flags);
 	offset = iommu_area_alloc(iommu_gart_bitmap, iommu_pages, next_bit,
-				  size, base_index, boundary_size, 0);
+				  size, base_index, boundary_size, size - 1);
 	if (offset == -1) {
 		need_flush = 1;
 		offset = iommu_area_alloc(iommu_gart_bitmap, iommu_pages, 0,
-					  size, base_index, boundary_size, 0);
+					  size, base_index, boundary_size,
+					  size - 1);
 	}
 	if (offset != -1) {
 		set_bit_string(iommu_gart_bitmap, offset, size);
diff --git a/lib/iommu-helper.c b/lib/iommu-helper.c
index a3b8d4c..b970f1b 100644
--- a/lib/iommu-helper.c
+++ b/lib/iommu-helper.c
@@ -16,7 +16,7 @@ again:
 	index = find_next_zero_bit(map, size, start);

 	/* Align allocation */
-	index = (index + align_mask) & ~align_mask;
+	index = (index + align_mask + 1) & ~align_mask;

 	end = index + nr;
 	if (end >= size)
--
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