dma-remap: support DMA_ATTR_NO_KERNEL_MAPPING
Do not waste vmalloc space on allocations that do not require a mapping
into the kernel address space.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
index dcc82dd..68a64e3 100644
--- a/kernel/dma/remap.c
+++ b/kernel/dma/remap.c
@@ -200,7 +200,8 @@
size = PAGE_ALIGN(size);
- if (!gfpflags_allow_blocking(flags)) {
+ if (!gfpflags_allow_blocking(flags) &&
+ !(attrs & DMA_ATTR_NO_KERNEL_MAPPING)) {
ret = dma_alloc_from_pool(size, &page, flags);
if (!ret)
return NULL;
@@ -215,6 +216,9 @@
/* remove any dirty cache lines on the kernel alias */
arch_dma_prep_coherent(page, size);
+ if (attrs & DMA_ATTR_NO_KERNEL_MAPPING)
+ return page; /* opaque cookie */
+
/* create a coherent mapping */
ret = dma_common_contiguous_remap(page, size, VM_USERMAP,
arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs),
@@ -227,7 +231,10 @@
void arch_dma_free(struct device *dev, size_t size, void *vaddr,
dma_addr_t dma_handle, unsigned long attrs)
{
- if (!dma_free_from_pool(vaddr, PAGE_ALIGN(size))) {
+ if (attrs & DMA_ATTR_NO_KERNEL_MAPPING) {
+ /* vaddr is a struct page cookie, not a kernel address */
+ __dma_direct_free_pages(dev, size, vaddr);
+ } else if (!dma_free_from_pool(vaddr, PAGE_ALIGN(size))) {
phys_addr_t phys = dma_to_phys(dev, dma_handle);
struct page *page = pfn_to_page(__phys_to_pfn(phys));
