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dma-direct: Restore arch_dma_alloc() for the DMA_ATTR_NO_KERNEL_MAPPING case

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Commit 849facea92 ("dma-direct: simplify the DMA_ATTR_NO_KERNEL_MAPPING
handling") moved the DMA_ATTR_NO_KERNEL_MAPPING shortcut in
dma_direct_alloc() in front of the arch_dma_alloc() call. Architectures
providing their own DMA coherent allocator (CONFIG_ARCH_HAS_DMA_ALLOC)
therefore no longer see such requests. ARM 32bit is one of such. Lack of
the call to arch_dma_alloc() results in the lack of proper cache
management on HighMem pages.

Take the dma-direct shortcut only for coherent devices or when the
architecture doesn't provide arch_dma_alloc(). While touching this,
move that check into separate function to avoid duplication in alloc
and free paths.

Fixes: 849facea92 ("dma-direct: simplify the DMA_ATTR_NO_KERNEL_MAPPING handling")
Reported-by: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Closes: https://lore.kernel.org/all/yq5ams2akznl.fsf@kernel.org/
Assisted-by: Claude Opus 5.5 <noreply@anthropic.com>
Link: https://lore.kernel.org/r/20260930135734.1013905-1-m.szyprowski@samsung.com
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
This commit is contained in:
Marek Szyprowski 2026-09-30 15:57:32 +02:00
parent 57a57ae077
commit 5e3bc6b44c
1 changed files with 18 additions and 4 deletions
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22
kernel/dma/direct.c
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@ -181,6 +181,22 @@ static struct page *dma_direct_alloc_from_pool(struct device *dev, size_t size,
return page;
}
/*
* Check if the allocation can skip the kernel mapping and return the page
* pointer as the cookie.
*/
static bool dma_direct_use_no_mapping(struct device *dev, unsigned long attrs)
{
if ((attrs & (DMA_ATTR_NO_KERNEL_MAPPING | __DMA_ATTR_ALLOC_CC_SHARED)) !=
DMA_ATTR_NO_KERNEL_MAPPING)
return false;
if (is_swiotlb_for_alloc(dev))
return false;
if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_ALLOC) && !dev_is_dma_coherent(dev))
return false;
return true;
}
static void *dma_direct_alloc_no_mapping(struct device *dev, size_t size,
dma_addr_t *dma_handle, gfp_t gfp)
{
@ -228,8 +244,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
if (attrs & DMA_ATTR_NO_WARN)
gfp |= __GFP_NOWARN;
if (((attrs & (DMA_ATTR_NO_KERNEL_MAPPING | __DMA_ATTR_ALLOC_CC_SHARED)) ==
DMA_ATTR_NO_KERNEL_MAPPING) && !is_swiotlb_for_alloc(dev))
if (dma_direct_use_no_mapping(dev, attrs))
return dma_direct_alloc_no_mapping(dev, size, dma_handle, gfp);
if (!dev_is_dma_coherent(dev)) {
@ -376,8 +391,7 @@ void dma_direct_free(struct device *dev, size_t size,
if (attrs & __DMA_ATTR_ALLOC_CC_SHARED)
mark_mem_encrypted = true;
if (((attrs & (DMA_ATTR_NO_KERNEL_MAPPING | __DMA_ATTR_ALLOC_CC_SHARED)) ==
DMA_ATTR_NO_KERNEL_MAPPING) && !is_swiotlb_for_alloc(dev)) {
if (dma_direct_use_no_mapping(dev, attrs)) {
/* cpu_addr is a struct page cookie, not a kernel address */
dma_free_contiguous(dev, cpu_addr, size);
return;