On Fri, 2008-05-09 at 20:55 +0200, Andrea Arcangeli wrote: > On Fri, May 09, 2008 at 08:37:29PM +0200, Peter Zijlstra wrote: > > Another possibility, would something like this work? > > > > > > /* > > * null out the begin function, no new begin calls can be made > > */ > > rcu_assing_pointer(my_notifier.invalidate_start_begin, NULL); > > > > /* > > * lock/unlock all rmap locks in any order - this ensures that any > > * pending start() will have its end() function called. > > */ > > mm_barrier(mm); > > > > /* > > * now that no new start() call can be made and all start()/end() pairs > > * are complete we can remove the notifier. > > */ > > mmu_notifier_remove(mm, my_notifier); > > > > > > This requires a mmu_notifier instance per attached mm and that > > __mmu_notifier_invalidate_range_start() uses rcu_dereference() to obtain > > the function. > > > > But I think its enough to ensure that: > > > > for each start an end will be called > > We don't need that, it's perfectly ok if start is called but end is > not, it's ok to unregister in the middle as I guarantee ->release is > called before mmu_notifier_unregister returns (if ->release is needed > at all, not the case for KVM/GRU). > > Unregister is already solved with srcu/rcu without any additional > complication as we don't need the guarantee that for each start an end > will be called. > > > It can however happen that end is called without start - but we could > > handle that I think. > > The only reason mm_lock() was introduced is to solve "register", to > guarantee that for each end there was a start. We can't handle end > called without start in the driver. > > The reason the driver must be prevented to register in the middle of > start/end, if that if it ever happens the driver has no way to know it > must stop the secondary mmu page faults to call get_user_pages and > instantiate sptes/secondarytlbs on pages that will be freed as soon as > zap_page_range starts.
Right - then I got it backwards. Never mind me then.. ------------------------------------------------------------------------- This SF.net email is sponsored by the 2008 JavaOne(SM) Conference Don't miss this year's exciting event. There's still time to save $100. Use priority code J8TL2D2. http://ad.doubleclick.net/clk;198757673;13503038;p?http://java.sun.com/javaone _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
