x86: enable DMA CMA with swiotlb

The DMA Contiguous Memory Allocator support on x86 is disabled when
swiotlb config option is enabled.  So DMA CMA is always disabled on
x86_64 because swiotlb is always enabled.  This attempts to support for
DMA CMA with enabling swiotlb config option.

The contiguous memory allocator on x86 is integrated in the function
dma_generic_alloc_coherent() which is .alloc callback in nommu_dma_ops
for dma_alloc_coherent().

x86_swiotlb_alloc_coherent() which is .alloc callback in swiotlb_dma_ops
tries to allocate with dma_generic_alloc_coherent() firstly and then
swiotlb_alloc_coherent() is called as a fallback.

The main part of supporting DMA CMA with swiotlb is that changing
x86_swiotlb_free_coherent() which is .free callback in swiotlb_dma_ops
for dma_free_coherent() so that it can distinguish memory allocated by
dma_generic_alloc_coherent() from one allocated by
swiotlb_alloc_coherent() and release it with dma_generic_free_coherent()
which can handle contiguous memory.  This change requires making
is_swiotlb_buffer() global function.

This also needs to change .free callback in the dma_map_ops for amd_gart
and sta2x11, because these dma_ops are also using
dma_generic_alloc_coherent().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: 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: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
index 6c483ba98b9c..77dd0ad58be4 100644
--- a/arch/x86/kernel/pci-swiotlb.c
+++ b/arch/x86/kernel/pci-swiotlb.c
@@ -14,7 +14,7 @@
 #include <asm/iommu_table.h>
 int swiotlb __read_mostly;
 
-static void *x86_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
+void *x86_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
 					dma_addr_t *dma_handle, gfp_t flags,
 					struct dma_attrs *attrs)
 {
@@ -28,11 +28,14 @@ static void *x86_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
 	return swiotlb_alloc_coherent(hwdev, size, dma_handle, flags);
 }
 
-static void x86_swiotlb_free_coherent(struct device *dev, size_t size,
+void x86_swiotlb_free_coherent(struct device *dev, size_t size,
 				      void *vaddr, dma_addr_t dma_addr,
 				      struct dma_attrs *attrs)
 {
-	swiotlb_free_coherent(dev, size, vaddr, dma_addr);
+	if (is_swiotlb_buffer(dma_to_phys(dev, dma_addr)))
+		swiotlb_free_coherent(dev, size, vaddr, dma_addr);
+	else
+		dma_generic_free_coherent(dev, size, vaddr, dma_addr, attrs);
 }
 
 static struct dma_map_ops swiotlb_dma_ops = {