On Thu, Feb 27, 2020 at 9:21 PM Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote: > > Hi, > > > > So I'd like to push patches 1+2 to -fixes and sort everything else later > > > in -next. OK? > > > > OK with me. > > Done. > > >> [ context: why shmem helpers use pgprot_writecombine + pgprot_decrypted? > >> we get conflicting mappings because of that, linear kernel > >> map vs. gem object vmap/mmap ] > > > Do we have any idea what drivers are actually using > > write-combine and decrypted? > > drivers/gpu/drm# find -name Kconfig* -print | xargs grep -l DRM_GEM_SHMEM_HELPER > ./lima/Kconfig > ./tiny/Kconfig > ./cirrus/Kconfig > ./Kconfig > ./panfrost/Kconfig > ./udl/Kconfig > ./v3d/Kconfig > ./virtio/Kconfig > > virtio needs cached. > cirrus+udl should be ok with cached too. > > Not clue about the others (lima, tiny, panfrost, v3d). Maybe they use > write-combine just because this is what they got by default from > drm_gem_mmap_obj(). Maybe they actually need that. Trying to Cc: > maintainters (and drop stable@). > lima driver needs writecombine mapped buffer for GPU hardware working properly due to CPU-GPU not cache coherent. Although we haven't meet problems caused by kernel/user map conflict, but I do admit it's a problem as I met with amdgpu+arm before. With TTM we can control page allocated and create a pool for writecombine pages, but seems shmem is not friendly with writecombine pages. Thanks, Qiang _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
