Messages in this thread | | | Date | Thu, 27 Feb 2020 11:56:43 +0100 | From | Gerd Hoffmann <> | Subject | Re: [PATCH v5 1/3] drm/shmem: add support for per object caching flags. |
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Hi,
> I think it might be safe for some integrated graphics where the driver > maintainers can guarantee that it's safe on all particular processors used > with that driver, but then IMO it should be moved out to those drivers. > > Other drivers needing write-combine shouldn't really use shmem. > > So again, to fix the regression, could we revert 0be895893607f ("drm/shmem: > switch shmem helper to &drm_gem_object_funcs.mmap") or does that have other > implications?
This patch isn't a regression. The old code path has the pgprot_writecombine() call in drm_gem_mmap_obj(), so the behavior is the same before and afterwards.
But with the patch in place we can easily have shmem helpers do their own thing instead of depending on whatever drm_gem_mmap_obj() is doing. Just using cached mappings unconditionally would be perfectly fine for virtio-gpu.
Not sure about the other users though. I'd like to fix the virtio-gpu regression (coming from ttm -> shmem switch) asap, and I don't feel like changing the behavior for other drivers in 5.6-rc is a good idea.
So I'd like to push patches 1+2 to -fixes and sort everything else later in -next. OK?
cheers, Gerd
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