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

Showing the changes to kernel (3 of 6 files). Show all

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3 files

kernel/dma/Kconfig +1 −6
kernel/dma/Makefile +1 −1
kernel/dma/direct.c +7 −11

kernel/dma/Kconfig+1−6

@@ -110,15 +110,10 @@ config DMA_GLOBAL_POOL · 109 unmodified lines
110	110	select DMA_DECLARE_COHERENT
111	111	bool
112	112
113		−config DMA_REMAP
114		− bool
115		− depends on MMU
116		− select DMA_NONCOHERENT_MMAP
117		−
118	113	config DMA_DIRECT_REMAP
119	114	bool
120		− select DMA_REMAP
121	115	select DMA_COHERENT_POOL
	116	+ select DMA_NONCOHERENT_MMAP
122	117
123	118	config DMA_CMA
124	119	bool "DMA Contiguous Memory Allocator"

kernel/dma/Makefile+1−1

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

kernel/dma/direct.c+7−11

@@ -265,17 +265,13 @@ void dma_direct_alloc(struct device dev, size_t size, · 264 unmodified lines
265	265	page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO);
266	266	if (!page)
267	267	return NULL;
	268	+
	269	+ /*
	270	+ * dma_alloc_contiguous can return highmem pages depending on a
	271	+ * combination the cma= arguments and per-arch setup. These need to be
	272	+ * remapped to return a kernel virtual address.
	273	+ */
268	274	if (PageHighMem(page)) {
269		− /*
270		− * Depending on the cma= arguments and per-arch setup,
271		− * dma_alloc_contiguous could return highmem pages.
272		− * Without remapping there is no way to return them here, so
273		− * log an error and fail.
274		− */
275		− if (!IS_ENABLED(CONFIG_DMA_REMAP)) {
276		− dev_info(dev, "Rejecting highmem page from CMA.\n");
277		− goto out_free_pages;
278		− }
279	275	remap = true;
280	276	set_uncached = false;
281	277	}
@@ -349,7 +345,7 @@ void dma_direct_free(struct device *dev, size_t size, · 67 unmodified lines
349	345	dma_free_from_pool(dev, cpu_addr, PAGE_ALIGN(size)))
350	346	return;
351	347
352		− if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) {
	348	+ if (is_vmalloc_addr(cpu_addr)) {
353	349	vunmap(cpu_addr);
354	350	} else {
355	351	if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CLEAR_UNCACHED))