On Tue, Jul 21, 2026 at 07:50:10PM +0530, Aneesh Kumar K.V wrote: > 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.
Can you please point to the code there it can happen? __dma_alloc_from_pool() has direct connection between physical address and struct page. Thanks > > -aneesh >
