On Tue, 22 Nov 2022 at 20:34, Jason Gunthorpe <jgg@xxxxxxxx> wrote: > On Tue, Nov 22, 2022 at 08:29:05PM +0100, Daniel Vetter wrote: > > You nuke all the ptes. Drivers that move have slightly more than a > > bare struct file, they also have a struct address_space so that > > invalidate_mapping_range() works. > > Okay, this is one of the ways that this can be made to work correctly, > as long as you never allow GUP/GUP_fast to succeed on the PTEs. (this > was the DAX mistake) Hence this patch, to enforce that no dma-buf exporter gets this wrong. Which some did, and then blamed bug reporters for the resulting splats :-) One of the things we've reverted was the ttm huge pte support, since that doesn't have the pmd_special flag (yet) and so would let gup_fast through. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
