[PATCH v7 04/22] dma: free atomic pool pages by physical address
From: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>
Date: 2026-07-01 05:50:28
Also in:
linux-arm-kernel, linux-coco, linux-iommu, linux-s390, lkml
Subsystem:
dma mapping helpers, the rest · Maintainers:
Marek Szyprowski, Linus Torvalds
dma_direct_alloc_pages() may satisfy atomic allocations from the coherent atomic pools. The pool allocation is keyed by the virtual address stored in the gen_pool, but the pages API returns only the backing struct page. On architectures with CONFIG_DMA_DIRECT_REMAP, atomic pool chunks are added to the gen_pool using their remapped virtual address. dma_direct_free_pages() reconstructs a linear-map address with page_address(page) and passes that to dma_free_from_pool(). That address does not match the gen_pool virtual range, so the pool lookup can fail and the code can fall through to freeing a pool-owned page through the normal page allocator path. Add a page-based pool free helper that looks up the owning pool chunk by physical address, translates it back to the gen_pool virtual address, and frees that address to the pool. Use it from dma_direct_free_pages() while keeping the existing virtual-address helper for coherent allocation frees. Tested-by: Michael Kelley <redacted> Tested-by: Mostafa Saleh <smostafa@google.com> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org> --- include/linux/dma-map-ops.h | 1 + kernel/dma/direct.c | 4 +-- kernel/dma/pool.c | 54 +++++++++++++++++++++++++++++++++++++ 3 files changed, 57 insertions(+), 2 deletions(-)
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index bcb5b5428aea..137e015c1750 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h@@ -215,6 +215,7 @@ struct page *dma_alloc_from_pool(struct device *dev, size_t size, void **cpu_addr, gfp_t flags, bool (*phys_addr_ok)(struct device *, phys_addr_t, size_t)); bool dma_free_from_pool(struct device *dev, void *start, size_t size); +bool dma_free_from_pool_page(struct device *dev, struct page *page, size_t size); int dma_direct_set_offset(struct device *dev, phys_addr_t cpu_start, dma_addr_t dma_start, u64 size);
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index b4cb2c03e5d7..17f1e097499e 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c@@ -381,9 +381,9 @@ void dma_direct_free_pages(struct device *dev, size_t size, { void *vaddr = page_address(page); - /* If cpu_addr is not from an atomic pool, dma_free_from_pool() fails */ + /* If page is not from an atomic pool, dma_free_from_pool_page() fails */ if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) && - dma_free_from_pool(dev, vaddr, size)) + dma_free_from_pool_page(dev, page, size)) return; if (dma_set_encrypted(dev, vaddr, size))
diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index b0303efbc153..76bcafe03e44 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c@@ -311,3 +311,57 @@ bool dma_free_from_pool(struct device *dev, void *start, size_t size) return false; } + +struct dma_pool_phys_match { + phys_addr_t phys; + size_t size; + unsigned long addr; + bool found; +}; + +static void dma_pool_find_phys(struct gen_pool *pool, struct gen_pool_chunk *chunk, + void *data) +{ + struct dma_pool_phys_match *match = data; + phys_addr_t end = match->phys + match->size - 1; + phys_addr_t chunk_end; + + if (match->found) + return; + + chunk_end = chunk->phys_addr + (chunk->end_addr - chunk->start_addr); + if (match->phys < chunk->phys_addr || end > chunk_end) + return; + + match->addr = chunk->start_addr + (match->phys - chunk->phys_addr); + match->found = true; +} + +static bool dma_free_from_pool_phys(struct gen_pool *pool, phys_addr_t phys, + size_t size) +{ + struct dma_pool_phys_match match = { + .phys = phys, + .size = size, + }; + + gen_pool_for_each_chunk(pool, dma_pool_find_phys, &match); + if (!match.found) + return false; + + gen_pool_free(pool, match.addr, size); + return true; +} + +bool dma_free_from_pool_page(struct device *dev, struct page *page, size_t size) +{ + struct gen_pool *pool = NULL; + phys_addr_t phys = page_to_phys(page); + + while ((pool = dma_guess_pool(pool, 0))) { + if (dma_free_from_pool_phys(pool, phys, size)) + return true; + } + + return false; +}
--
2.43.0