On Wed, Jul 10, 2024 at 04:14:18PM +0200, Christian König wrote: > Am 10.07.24 um 15:57 schrieb Lei Liu: > > Use vm_insert_page to establish a mapping for the memory allocated > > by dmabuf, thus supporting direct I/O read and write; and fix the > > issue of incorrect memory statistics after mapping dmabuf memory. > > Well big NAK to that! Direct I/O is intentionally disabled on DMA-bufs. > > We already discussed enforcing that in the DMA-buf framework and this patch > probably means that we should really do that. Last time I looked dma_mmap doesn't guarantee that the vma end sup with VM_SPECIAL, and that's pretty much the only reason why we can't enforce this. But we might be able to enforce this at least on some architectures, I didn't check for that ... if at least x86-64 and arm64 could have the check, that would be great. So might be worth it to re-audit this all. I think all other dma-buf exporters/allocators do only create VM_SPECIAL vmas. -Sima -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
