On Mon, 21 Jul 2008 10:15:27 -0400
Prarit Bhargava <prarit@xxxxxxxxxx> wrote:
> 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@xxxxxxxxxx>
>
> 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);
> }
This affects map_sg and map_single unnecessarily.
> 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;
Doesn't look right. What we do here is __ALIGN_MASK().
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