On Tue, May 12, 2026 at 02:33:56PM +0530, Aneesh Kumar K.V (Arm) wrote: > Move swiotlb allocation out of __dma_direct_alloc_pages() and handle it in > dma_direct_alloc() / dma_direct_alloc_pages(). > > This is needed for follow-up changes that simplify the handling of > memory encryption/decryption based on the DMA attribute flags. > > swiotlb backing pages are already mapped decrypted by > swiotlb_update_mem_attributes() and rmem_swiotlb_device_init(), so > dma-direct should not call dma_set_decrypted() on allocation nor > dma_set_encrypted() on free for swiotlb-backed memory. > > Update alloc/free paths to detect swiotlb-backed pages and skip > encrypt/decrypt transitions for those paths. Keep the existing highmem > rejection in dma_direct_alloc_pages() for swiotlb allocations. > > Only for "restricted-dma-pool", we currently set `for_alloc = true`, while > rmem_swiotlb_device_init() decrypts the whole pool up front. This pool is > typically used together with "shared-dma-pool", where the shared region is > accessed after remap/ioremap and the returned address is suitable for > decrypted memory access. So existing code paths remain valid. > > Signed-off-by: Aneesh Kumar K.V (Arm) <[email protected]> > --- > kernel/dma/direct.c | 44 +++++++++++++++++++++++++++++++++++++------- > 1 file changed, 37 insertions(+), 7 deletions(-) > > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > index ec887f443741..b958f150718a 100644 > --- a/kernel/dma/direct.c > +++ b/kernel/dma/direct.c > @@ -125,9 +125,6 @@ static struct page *__dma_direct_alloc_pages(struct > device *dev, size_t size, > > WARN_ON_ONCE(!PAGE_ALIGNED(size)); > > - if (is_swiotlb_for_alloc(dev)) > - return dma_direct_alloc_swiotlb(dev, size); > - > gfp |= dma_direct_optimal_gfp_mask(dev, &phys_limit); > page = dma_alloc_contiguous(dev, size, gfp); > if (page) { > @@ -204,6 +201,7 @@ void *dma_direct_alloc(struct device *dev, size_t size, > dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs) > { > bool remap = false, set_uncached = false; > + bool mark_mem_decrypt = true; > struct page *page; > void *ret; > > @@ -250,11 +248,21 @@ void *dma_direct_alloc(struct device *dev, size_t size, > dma_direct_use_pool(dev, gfp)) > return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp); > > + if (is_swiotlb_for_alloc(dev)) { > + page = dma_direct_alloc_swiotlb(dev, size); > + if (page) { > + mark_mem_decrypt = false; > + goto setup_page; > + } > + return NULL; > + } > + > /* we always manually zero the memory once we are done */ > page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO, true); > if (!page) > return NULL; > > +setup_page: > /* > * dma_alloc_contiguous can return highmem pages depending on a > * combination the cma= arguments and per-arch setup. These need to be > @@ -281,7 +289,7 @@ void *dma_direct_alloc(struct device *dev, size_t size, > goto out_free_pages; > } else { > ret = page_address(page); > - if (dma_set_decrypted(dev, ret, size)) > + if (mark_mem_decrypt && dma_set_decrypted(dev, ret, size))
I am ok with that approach, but Jason was mentioning we shouldn’t special case swiotlb and make the allocator return the memory state (similar to the dma_page [1]) . I am also OK if you want to merge that part of my series with is. [1] https://lore.kernel.org/linux-iommu/[email protected]/ > goto out_leak_pages; > } > > @@ -298,7 +306,7 @@ void *dma_direct_alloc(struct device *dev, size_t size, > return ret; > > out_encrypt_pages: > - if (dma_set_encrypted(dev, page_address(page), size)) > + if (mark_mem_decrypt && dma_set_encrypted(dev, page_address(page), > size)) > return NULL; > out_free_pages: > __dma_direct_free_pages(dev, page, size); > @@ -310,6 +318,7 @@ void *dma_direct_alloc(struct device *dev, size_t size, > void dma_direct_free(struct device *dev, size_t size, > void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs) > { > + bool mark_mem_encrypted = true; > unsigned int page_order = get_order(size); > > if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) && > @@ -338,12 +347,15 @@ void dma_direct_free(struct device *dev, size_t size, > dma_free_from_pool(dev, cpu_addr, PAGE_ALIGN(size))) > return; > > + if (swiotlb_find_pool(dev, dma_to_phys(dev, dma_addr))) > + mark_mem_encrypted = false; > + > if (is_vmalloc_addr(cpu_addr)) { > vunmap(cpu_addr); > } else { > if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CLEAR_UNCACHED)) > arch_dma_clear_uncached(cpu_addr, size); > - if (dma_set_encrypted(dev, cpu_addr, size)) > + if (mark_mem_encrypted && dma_set_encrypted(dev, cpu_addr, > size)) > return; > } > > @@ -359,6 +371,19 @@ struct page *dma_direct_alloc_pages(struct device *dev, > size_t size, > if (force_dma_unencrypted(dev) && dma_direct_use_pool(dev, gfp)) > return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp); > > + if (is_swiotlb_for_alloc(dev)) { > + page = dma_direct_alloc_swiotlb(dev, size); > + if (!page) > + return NULL; > + > + if (PageHighMem(page)) { My understanding is that rmem_swiotlb_device_init() asserts that there is no PageHighMem()? Also a similar check doesn’t exist in dma_direct_alloc(). Thanks, Mostafa > + swiotlb_free(dev, page, size); > + return NULL; > + } > + ret = page_address(page); > + goto setup_page; > + } > + > page = __dma_direct_alloc_pages(dev, size, gfp, false); > if (!page) > return NULL; > @@ -366,6 +391,7 @@ struct page *dma_direct_alloc_pages(struct device *dev, > size_t size, > ret = page_address(page); > if (dma_set_decrypted(dev, ret, size)) > goto out_leak_pages; > +setup_page: > memset(ret, 0, size); > *dma_handle = phys_to_dma_direct(dev, page_to_phys(page)); > return page; > @@ -378,13 +404,17 @@ void dma_direct_free_pages(struct device *dev, size_t > size, > enum dma_data_direction dir) > { > void *vaddr = page_address(page); > + bool mark_mem_encrypted = true; > > /* If cpu_addr is not from an atomic pool, dma_free_from_pool() fails */ > if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) && > dma_free_from_pool(dev, vaddr, size)) > return; > > - if (dma_set_encrypted(dev, vaddr, size)) > + if (swiotlb_find_pool(dev, page_to_phys(page))) > + mark_mem_encrypted = false; > + > + if (mark_mem_encrypted && dma_set_encrypted(dev, vaddr, size)) > return; > __dma_direct_free_pages(dev, page, size); > } > -- > 2.43.0 >
