Leon Romanovsky <[email protected]> writes: > On Fri, Jul 17, 2026 at 11:34:19PM +0530, Aneesh Kumar K.V (Arm) wrote: >> Commit 5b138c534fda ("dma-direct: factor out a dma_direct_alloc_from_pool >> helper") changed dma_direct_alloc_from_pool() to return the CPU address >> from dma_alloc_from_pool(). That fits dma_direct_alloc(), but >> dma_direct_alloc_pages() also uses the helper and expects a struct page *. >> >> Fix this by making dma_direct_alloc_from_pool() return the struct page * >> again, and pass the CPU address back through an out-parameter for the >> dma_direct_alloc() caller. >> >> Fixes: 5b138c534fda ("dma-direct: factor out a dma_direct_alloc_from_pool >> helper") >> Cc: [email protected] >> Tested-by: Michael Kelley <[email protected]> >> Tested-by: Mostafa Saleh <[email protected]> >> Reviewed-by: Jason Gunthorpe <[email protected]> >> Signed-off-by: Aneesh Kumar K.V (Arm) <[email protected]> >> --- >> kernel/dma/direct.c | 18 ++++++++++-------- >> 1 file changed, 10 insertions(+), 8 deletions(-) >> >> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c >> index d8219efe3273..363d984d90e7 100644 >> --- a/kernel/dma/direct.c >> +++ b/kernel/dma/direct.c >> @@ -164,22 +164,21 @@ static bool dma_direct_use_pool(struct device *dev, >> gfp_t gfp) >> return !gfpflags_allow_blocking(gfp) && !is_swiotlb_for_alloc(dev); >> } >> >> -static void *dma_direct_alloc_from_pool(struct device *dev, size_t size, >> - dma_addr_t *dma_handle, gfp_t gfp) >> +static struct page *dma_direct_alloc_from_pool(struct device *dev, size_t >> size, >> + dma_addr_t *dma_handle, void **cpu_addr, gfp_t gfp) >> { >> struct page *page; >> u64 phys_limit; >> - void *ret; >> >> if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_DMA_COHERENT_POOL))) >> return NULL; >> >> gfp |= dma_direct_optimal_gfp_mask(dev, &phys_limit); >> - page = dma_alloc_from_pool(dev, size, &ret, gfp, dma_coherent_ok); >> + page = dma_alloc_from_pool(dev, size, cpu_addr, gfp, dma_coherent_ok); >> if (!page) >> return NULL; >> *dma_handle = phys_to_dma_direct(dev, page_to_phys(page)); >> - return ret; >> + return page; >> } >> >> static void *dma_direct_alloc_no_mapping(struct device *dev, size_t size, >> @@ -247,8 +246,11 @@ void *dma_direct_alloc(struct device *dev, size_t size, >> * the atomic pools instead if we aren't allowed block. >> */ >> if ((remap || force_dma_unencrypted(dev)) && >> - dma_direct_use_pool(dev, gfp)) >> - return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp); >> + dma_direct_use_pool(dev, gfp)) { >> + page = dma_direct_alloc_from_pool(dev, size, dma_handle, >> + &ret, gfp); >> + return page ? ret : NULL; > > Sorry for joining the discussion late, but the line above caught my > attention. > > Why do we need both ret and page? We can derive cpu_addr from page and > vice versa. Do we really need the &ret parameter? Or, more generally, do > we really need "struct page *"? > > static struct page *__dma_alloc_from_pool(struct device *dev, size_t size, > struct gen_pool *pool, void **cpu_addr, > bool (*phys_addr_ok)(struct device *, phys_addr_t, size_t)) > { > ... > *cpu_addr = (void *)addr; > memset(*cpu_addr, 0, size); > return pfn_to_page(__phys_to_pfn(phys)); > } > > Why >
With CONFIG_DMA_DIRECT_REMAP the cpu_addr can be different from page_address. -aneesh
