[PATCH] x86: restore the old swiotlb alloc_coherent behavior

[PATCH] x86: restore the old swiotlb alloc_coherent behavior

[FUJITA Tomonori]

This restores the old swiotlb alloc_coherent behavior (before the
alloc_coherent rewrite):

http://lkml.org/lkml/2008/8/12/200

The old alloc_coherent avoids GFP_DMA allocation first and if the
allocated address is not fit for the device's coherent_dma_mask, then
dma_alloc_coherent does GFP_DMA allocation. If it fails,
alloc_coherent calls swiotlb_alloc_coherent (in short, we rarely used
swiotlb_alloc_coherent).

After the alloc_coherent rewrite, dma_alloc_coherent
(include/asm-x86/dma-mapping.h) directly calls swiotlb_alloc_coherent.
It means that we possibly can't handle a device having dma_masks >
24bit < 32bits since swiotlb_alloc_coherent doesn't have the above
GFP_DMA retry mechanism.

This patch fixes x86's swiotlb alloc_coherent to use the GFP_DMA retry
mechanism, which dma_generic_alloc_coherent() provides now
(pci-nommu.c and GART IOMMU driver also use
dma_generic_alloc_coherent).

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
---
 arch/x86/kernel/pci-swiotlb_64.c |   14 +++++++++++++-
 1 files changed, 13 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/pci-swiotlb_64.c b/arch/x86/kernel/pci-swiotlb_64.c
index c4ce033..3c539d1 100644
--- a/arch/x86/kernel/pci-swiotlb_64.c
+++ b/arch/x86/kernel/pci-swiotlb_64.c
@@ -18,9 +18,21 @@ swiotlb_map_single_phys(struct device *hwdev, phys_addr_t paddr, size_t size,
 	return swiotlb_map_single(hwdev, phys_to_virt(paddr), size, direction);
 }
 
+static void *x86_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
+					dma_addr_t *dma_handle, gfp_t flags)
+{
+	void *vaddr;
+
+	vaddr = dma_generic_alloc_coherent(hwdev, size, dma_handle, flags);
+	if (vaddr)
+		return vaddr;
+
+	return swiotlb_alloc_coherent(hwdev, size, dma_handle, flags);
+}
+
 struct dma_mapping_ops swiotlb_dma_ops = {
 	.mapping_error = swiotlb_dma_mapping_error,
-	.alloc_coherent = swiotlb_alloc_coherent,
+	.alloc_coherent = x86_swiotlb_alloc_coherent,
 	.free_coherent = swiotlb_free_coherent,
 	.map_single = swiotlb_map_single_phys,
 	.unmap_single = swiotlb_unmap_single,
-- 
1.5.5.GIT

Re: [PATCH] x86: restore the old swiotlb alloc_coherent behavior

[Ingo Molnar]

* FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:

> This restores the old swiotlb alloc_coherent behavior (before the
> alloc_coherent rewrite):
> 
> http://lkml.org/lkml/2008/8/12/200
> 
> The old alloc_coherent avoids GFP_DMA allocation first and if the
> allocated address is not fit for the device's coherent_dma_mask, then
> dma_alloc_coherent does GFP_DMA allocation. If it fails,
> alloc_coherent calls swiotlb_alloc_coherent (in short, we rarely used
> swiotlb_alloc_coherent).
> 
> After the alloc_coherent rewrite, dma_alloc_coherent
> (include/asm-x86/dma-mapping.h) directly calls swiotlb_alloc_coherent.
> It means that we possibly can't handle a device having dma_masks >
> 24bit < 32bits since swiotlb_alloc_coherent doesn't have the above
> GFP_DMA retry mechanism.
> 
> This patch fixes x86's swiotlb alloc_coherent to use the GFP_DMA retry
> mechanism, which dma_generic_alloc_coherent() provides now
> (pci-nommu.c and GART IOMMU driver also use
> dma_generic_alloc_coherent).
> 
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> ---
>  arch/x86/kernel/pci-swiotlb_64.c |   14 +++++++++++++-
>  1 files changed, 13 insertions(+), 1 deletions(-)

applied to tip/core/urgent (to after the two other iommu related 
patches) - thanks Fujita!

	Ingo