On Thu, Jun 26, 2025 at 07:43:06PM +0200, Alexander Potapenko wrote: > On Wed, Jun 25, 2025 at 3:19 PM Leon Romanovsky <l...@kernel.org> wrote: > > > > From: Leon Romanovsky <leo...@nvidia.com> > > Hi Leon, > > > > > Convert the KMSAN DMA handling function from page-based to physical > > address-based interface. > > > > The refactoring renames kmsan_handle_dma() parameters from accepting > > (struct page *page, size_t offset, size_t size) to (phys_addr_t phys, > > size_t size). > > Could you please elaborate a bit why this is needed? Are you fixing > some particular issue?
It is soft of the fix and improvement at the same time. Improvement: It allows direct call to kmsan_handle_dma() without need to convert from phys_addr_t to struct page for newly introduced dma_map_phys() routine. Fix: It prevents us from executing kmsan for addresses that don't have struct page (for example PCI_P2PDMA_MAP_THRU_HOST_BRIDGE pages), which we are doing with original code. dma_map_sg_attrs() -> __dma_map_sg_attrs() -> dma_direct_map_sg() -> PCI_P2PDMA_MAP_THRU_HOST_BRIDGE and nents > 0 -> kmsan_handle_dma_sg(); -> kmsan_handle_dma(g_page(item) <---- this is "fake" page. We are trying to build DMA API that doesn't require struct pages. > > > A PFN_VALID check is added to prevent KMSAN operations > > on non-page memory, preventing from non struct page backed address, > > > > As part of this change, support for highmem addresses is implemented > > using kmap_local_page() to handle both lowmem and highmem regions > > properly. All callers throughout the codebase are updated to use the > > new phys_addr_t based interface. > > KMSAN only works on 64-bit systems, do we actually have highmem on any of > these? I don't know, but the original code had this check: 344 if (PageHighMem(page)) 345 return; Thanks