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dma-direct: refactor the !coherent checks in dma_direct_alloc

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Add a big central !dev_is_dma_coherent(dev) block to deal with as much
as of the uncached allocation schemes and document the schemes a bit
better.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
This commit is contained in:
Christoph Hellwig 2021-10-21 09:47:31 +02:00
parent d541ae55d5
commit a86d10942d
1 changed files with 41 additions and 25 deletions
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66
kernel/dma/direct.c
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@ -201,29 +201,49 @@ void *dma_direct_alloc(struct device *dev, size_t size,
!force_dma_unencrypted(dev) && !is_swiotlb_for_alloc(dev))
return dma_direct_alloc_no_mapping(dev, size, dma_handle, gfp);
if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) &&
!IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
!IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) &&
!dev_is_dma_coherent(dev) &&
!is_swiotlb_for_alloc(dev))
return arch_dma_alloc(dev, size, dma_handle, gfp, attrs);
if (!dev_is_dma_coherent(dev)) {
/*
* Fallback to the arch handler if it exists. This should
* eventually go away.
*/
if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) &&
!IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
!IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) &&
!is_swiotlb_for_alloc(dev))
return arch_dma_alloc(dev, size, dma_handle, gfp,
attrs);
if (IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) &&
!dev_is_dma_coherent(dev))
return dma_alloc_from_global_coherent(dev, size, dma_handle);
/*
* If there is a global pool, always allocate from it for
* non-coherent devices.
*/
if (IS_ENABLED(CONFIG_DMA_GLOBAL_POOL))
return dma_alloc_from_global_coherent(dev, size,
dma_handle);
/*
* Otherwise remap if the architecture is asking for it. But
* given that remapping memory is a blocking operation we'll
* instead have to dip into the atomic pools.
*/
remap = IS_ENABLED(CONFIG_DMA_DIRECT_REMAP);
if (remap) {
if (!gfpflags_allow_blocking(gfp) &&
!is_swiotlb_for_alloc(dev))
return dma_direct_alloc_from_pool(dev, size,
dma_handle, gfp);
} else {
if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED))
set_uncached = true;
}
}
/*
* Remapping or decrypting memory may block. If either is required and
* we can't block, allocate the memory from the atomic pools.
* If restricted DMA (i.e., is_swiotlb_for_alloc) is required, one must
* set up another device coherent pool by shared-dma-pool and use
* dma_alloc_from_dev_coherent instead.
* Decrypting memory may block, so allocate the memory from the atomic
* pools if we can't block.
*/
if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) &&
!gfpflags_allow_blocking(gfp) &&
(force_dma_unencrypted(dev) ||
(IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
!dev_is_dma_coherent(dev))) &&
force_dma_unencrypted(dev) && !gfpflags_allow_blocking(gfp) &&
!is_swiotlb_for_alloc(dev))
return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
@ -231,10 +251,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO);
if (!page)
return NULL;
if (!dev_is_dma_coherent(dev) && IS_ENABLED(CONFIG_DMA_DIRECT_REMAP)) {
remap = true;
} else if (PageHighMem(page)) {
if (PageHighMem(page)) {
/*
* Depending on the cma= arguments and per-arch setup,
* dma_alloc_contiguous could return highmem pages.
@ -246,9 +263,8 @@ void *dma_direct_alloc(struct device *dev, size_t size,
goto out_free_pages;
}
remap = true;
} else if (!dev_is_dma_coherent(dev) &&
IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED))
set_uncached = true;
set_uncached = false;
}
if (remap) {
/* remove any dirty cache lines on the kernel alias */