On Wed, 20 Feb 2008, Nick Piggin wrote: > On Friday 15 February 2008 17:49, Christoph Lameter wrote: > > The invalidation of address ranges in a mm_struct needs to be > > performed when pages are removed or permissions etc change. > > > > If invalidate_range_begin() is called with locks held then we > > pass a flag into invalidate_range() to indicate that no sleeping is > > possible. Locks are only held for truncate and huge pages. > > You can't sleep inside rcu_read_lock()!
Could you be specific? This refers to page migration? Hmmm... Guess we would need to inc the refcount there instead? > I must say that for a patch that is up to v8 or whatever and is > posted twice a week to such a big cc list, it is kind of slack to > not even test it and expect other people to review it. It was tested with the GRU and XPmem. Andrea also reported success. > Also, what we are going to need here are not skeleton drivers > that just do all the *easy* bits (of registering their callbacks), > but actual fully working examples that do everything that any > real driver will need to do. If not for the sanity of the driver > writer, then for the sanity of the VM developers (I don't want > to have to understand xpmem or infiniband in order to understand > how the VM works). There are 3 different drivers that can already use it but the code is complex and not easy to review. Skeletons are easy to allow people to get started with it. > > lru_add_drain(); > > tlb = tlb_gather_mmu(mm, 0); > > update_hiwater_rss(mm); > > + mmu_notifier(invalidate_range_begin, mm, address, end, atomic); > > end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details); > > if (tlb) > > tlb_finish_mmu(tlb, address, end); > > + mmu_notifier(invalidate_range_end, mm, address, end, atomic); > > return end; > > } > > > > Where do you invalidate for munmap()? zap_page_range() called from unmap_vmas(). > Also, how to you resolve the case where you are not allowed to sleep? > I would have thought either you have to handle it, in which case nobody > needs to sleep; or you can't handle it, in which case the code is > broken. That can be done in a variety of ways: 1. Change VM locking 2. Not handle file backed mappings (XPmem could work mostly in such a config) 3. Keep the refcount elevated until pages are freed in another execution context. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
