dma-mapping: remove CONFIG_DMA_REMAP

CONFIG_DMA_REMAP is used to build a few helpers around the core vmalloc code, and to use them in case there is a highmem page in dma-direct, and to make dma coherent allocations be able to use non-contiguous pages allocations for DMA allocations in the dma-iommu layer. Right now it needs to be explicitly selected by architectures, and is only done so by architectures that require remapping to deal with devices that are not DMA coherent. Make it unconditional for builds with CONFIG_MMU as it is very little extra code, but makes it much more likely that large DMA allocations succeed on x86. This fixes hot plugging a NVMe thunderbolt SSD for me, which tries to allocate a 1MB buffer that is otherwise hard to obtain due to memory fragmentation on a heavily used laptop.

Christoph Hellwig committed 4 years ago

Commit f5ff79f1 parent fba09096 files · +16 −29Browse files

Unified · Split

6 files

arch/arm/Kconfig +1 −1
arch/xtensa/Kconfig +1 −1
drivers/iommu/dma-iommu.c +5 −9
kernel/dma/Kconfig +1 −6
kernel/dma/Makefile +1 −1
kernel/dma/direct.c +7 −11

arch/arm/Kconfig+1−1

@@ -47,7 +47,7 @@ config ARM · 46 unmodified lines
47	select DMA_DECLARE_COHERENT	47	select DMA_DECLARE_COHERENT
48	select DMA_GLOBAL_POOL if !MMU	48	select DMA_GLOBAL_POOL if !MMU
49	select DMA_OPS	49	select DMA_OPS
50	select DMA_REMAP if MMU	50	select DMA_NONCOHERENT_MMAP if MMU
51	select EDAC_SUPPORT	51	select EDAC_SUPPORT
52	select EDAC_ATOMIC_SCRUB	52	select EDAC_ATOMIC_SCRUB
53	select GENERIC_ALLOCATOR	53	select GENERIC_ALLOCATOR

arch/xtensa/Kconfig+1−1

@@ -17,7 +17,7 @@ config XTENSA · 16 unmodified lines
17	select BUILDTIME_TABLE_SORT	17	select BUILDTIME_TABLE_SORT
18	select CLONE_BACKWARDS	18	select CLONE_BACKWARDS
19	select COMMON_CLK	19	select COMMON_CLK
20	select DMA_REMAP if MMU	20	select DMA_NONCOHERENT_MMAP if MMU
21	select GENERIC_ATOMIC64	21	select GENERIC_ATOMIC64
22	select GENERIC_IRQ_SHOW	22	select GENERIC_IRQ_SHOW
23	select GENERIC_PCI_IOMAP	23	select GENERIC_PCI_IOMAP

drivers/iommu/dma-iommu.c+5−9

 	return NULL;
 }
-#ifdef CONFIG_DMA_REMAP
 static struct sg_table *iommu_dma_alloc_noncontiguous(struct device *dev,
 		size_t size, enum dma_data_direction dir, gfp_t gfp,
 		unsigned long attrs)
 	sg_free_table(&sh->sgt);
 	kfree(sh);
 }
-#endif /* CONFIG_DMA_REMAP */
 static void iommu_dma_sync_single_for_cpu(struct device *dev,
 		dma_addr_t dma_handle, size_t size, enum dma_data_direction dir)
 	    dma_free_from_pool(dev, cpu_addr, alloc_size))
 		return;
-	if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) {
+	if (is_vmalloc_addr(cpu_addr)) {
 		/*
 		 * If it the address is remapped, then it's either non-coherent
 		 * or highmem CMA, or an iommu_dma_alloc_remap() construction.
 	if (!page)
 		return NULL;
-	if (IS_ENABLED(CONFIG_DMA_REMAP) && (!coherent || PageHighMem(page))) {
+	if (!coherent || PageHighMem(page)) {
 		pgprot_t prot = dma_pgprot(dev, PAGE_KERNEL, attrs);
 		cpu_addr = dma_common_contiguous_remap(page, alloc_size,
 	gfp |= __GFP_ZERO;
-	if (IS_ENABLED(CONFIG_DMA_REMAP) && gfpflags_allow_blocking(gfp) &&
+	if (gfpflags_allow_blocking(gfp) &&
 	    !(attrs & DMA_ATTR_FORCE_CONTIGUOUS)) {
 		return iommu_dma_alloc_remap(dev, size, handle, gfp,
 				dma_pgprot(dev, PAGE_KERNEL, attrs), attrs);
 	if (off >= nr_pages || vma_pages(vma) > nr_pages - off)
 		return -ENXIO;
-	if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) {
+	if (is_vmalloc_addr(cpu_addr)) {
 		struct page **pages = dma_common_find_pages(cpu_addr);
 		if (pages)
 	struct page *page;
 	int ret;
-	if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) {
+	if (is_vmalloc_addr(cpu_addr)) {
 		struct page **pages = dma_common_find_pages(cpu_addr);
 		if (pages) {
 	.free			= iommu_dma_free,
 	.alloc_pages		= dma_common_alloc_pages,
 	.free_pages		= dma_common_free_pages,
-#ifdef CONFIG_DMA_REMAP
 	.alloc_noncontiguous	= iommu_dma_alloc_noncontiguous,
 	.free_noncontiguous	= iommu_dma_free_noncontiguous,
-#endif
 	.mmap			= iommu_dma_mmap,
 	.get_sgtable		= iommu_dma_get_sgtable,
 	.map_page		= iommu_dma_map_page,

kernel/dma/Kconfig+1−6

 	select DMA_DECLARE_COHERENT
 	bool
-config DMA_REMAP
-	bool
-	depends on MMU
-	select DMA_NONCOHERENT_MMAP
 config DMA_DIRECT_REMAP
 	bool
-	select DMA_REMAP
 	select DMA_COHERENT_POOL
+	select DMA_NONCOHERENT_MMAP
 config DMA_CMA
 	bool "DMA Contiguous Memory Allocator"

kernel/dma/Makefile+1−1

@@ -8,5 +8,5 @@ obj-$(CONFIG_DMA_DECLARE_COHERENT) += coherent.o · 7 unmodified lines
8	obj-$(CONFIG_DMA_API_DEBUG) += debug.o	8	obj-$(CONFIG_DMA_API_DEBUG) += debug.o
9	obj-$(CONFIG_SWIOTLB) += swiotlb.o	9	obj-$(CONFIG_SWIOTLB) += swiotlb.o
10	obj-$(CONFIG_DMA_COHERENT_POOL) += pool.o	10	obj-$(CONFIG_DMA_COHERENT_POOL) += pool.o
11	obj-$(CONFIG_DMA_REMAP) += remap.o	11	obj-$(CONFIG_MMU) += remap.o
12	obj-$(CONFIG_DMA_MAP_BENCHMARK) += map_benchmark.o	12	obj-$(CONFIG_DMA_MAP_BENCHMARK) += map_benchmark.o

kernel/dma/direct.c+7−11

 	page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO);
 	if (!page)
 		return NULL;
+	/*
+	 * dma_alloc_contiguous can return highmem pages depending on a
+	 * combination the cma= arguments and per-arch setup.  These need to be
+	 * remapped to return a kernel virtual address.
+	 */
 	if (PageHighMem(page)) {
-		/*
-		 * Depending on the cma= arguments and per-arch setup,
-		 * dma_alloc_contiguous could return highmem pages.
-		 * Without remapping there is no way to return them here, so
-		 * log an error and fail.
-		 */
-		if (!IS_ENABLED(CONFIG_DMA_REMAP)) {
-			dev_info(dev, "Rejecting highmem page from CMA.\n");
-			goto out_free_pages;
-		}
 		remap = true;
 		set_uncached = false;
 	}
 	    dma_free_from_pool(dev, cpu_addr, PAGE_ALIGN(size)))
 		return;
-	if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) {
+	if (is_vmalloc_addr(cpu_addr)) {
 		vunmap(cpu_addr);
 	} else {
 		if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CLEAR_UNCACHED))