On Mon, May 18, 2020 at 10:50:15AM +0200, Thomas Zimmermann wrote: > Hi Gerd > > Am 18.05.20 um 10:23 schrieb Gerd Hoffmann: > >>> $ git grep drm_gem_shmem_mmap > >>> > >>> We also need correct access from userspace, otherwise the gpu is going to > >>> be sad. > >> > >> I've been thinking about this, and I think it means that we can never > >> have cached mappings anywhere. Even if shmem supports it internally for > >> most drivers, as soon as the page are exported, the importer could > >> expect uncached memory. > > > > The importer should not expect anything but call dma-buf ops so the > > exporter has a chance to handle this correctly. > > I have the following case in mind: Suppose the exporter maps cached > pages and the importer expects uncached pages for DMA. There is > map_dma_buf/unmap_dma_buf, which can implement a cache flush for the > cached pages. Is it guaranteed that the importer calls this around each > DMA operation? I think the importer is supposed to do that, but I wouldn't surprised if there are cases in tree where this isn't implemented correctly ... take care, Gerd _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
