Hey Chris, recently I had a look at i915_gem_userptr.c in order to extend the mmu_notifier call-backs implemented there. My goal is to implement the change_pte call-back where it is necessary to get rid of it being wrapped mn_invalidate_range_start/end() calls (for the reason see commit 6bdb913f). For most users of mmu_notifiers this is easy, except the i915 driver :) The invalidate_range_start notifier implemented there can sleep, so it can't be reused for a change_pte implementation (because change_pte is called under ptl spin_lock and is not allowed to sleep). On the other hand you also didn't implement the invalidate_page notifier, so I am not sure whether the code actually cares about the somewhat similar change_pte events? Here is where change_pte is called from: * In KSM code when pages are merged (shouldn't be relevant because KSM doesn't merged pages returned by get_user_pages()) * In uprobes code when a user-page is replaced by a kernel page (should only handle .text sections, so probaly not relevant here) * When someone writes to a COW page in mm/memory.c (this looks relevant looking at forked processes, on the other hand, this is currently handled by unbinding the vma from the object list in the i915 driver) I am not familiar with the i915 hardware and the driver implementation details, so I wanted to ask whether the driver 1) Cares about the change_pte event? 2) If it cares, what is the best way to implement it? What the invalidate_range_start() notifier does seems a bit overkill, since for the change_pte event nothing is unmapped (but maybe remapped) So any insight you could provide here would be useful :) Thanks, Joerg _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
