On Wed, Apr 02, 2008 at 10:59:50AM -0700, Christoph Lameter wrote: > Did I see #v10? Could you start a new subject when you post please? Do > not respond to some old message otherwise the threading will be wrong.
I wasn't clear enough, #v10 was in the works... I was thinking about the last two issues before posting it. > How exactly does the GRU corrupt memory? Jack added synchronize_rcu, I assume for a reason. > > > Another less obviously safe approach is to allow the register > > method to succeed only when mm_users=1 and the task is single > > threaded. This way if all the places where the mmu notifers aren't > > invoked on the mm not by the current task, are only doing > > invalidates after/before zapping ptes, if the istantiation of new > > ptes is single threaded too, we shouldn't worry if we miss an > > invalidate for a pte that is zero and doesn't point to any physical > > page. In the places where current->mm != mm I'm using > > invalidate_page 99% of the time, and that only follows the > > ptep_clear_flush. The problem are the range_begin that will happen > > before zapping the pte in places where current->mm != > > mm. Unfortunately in my incremental patch where I move all > > invalidate_page outside of the PT lock to prepare for allowing > > sleeping inside the mmu notifiers, I used range_begin/end in places > > like try_to_unmap_cluster where current->mm != mm. In general > > this solution looks more fragile than the seqlock. > > Hmmm... Okay that is one solution that would just require a BUG_ON in the > registration methods. Perhaps you didn't notice that this solution can't work if you call range_begin/end not in the "current" context and try_to_unmap_cluster does exactly that for both my patchset and yours. Missing an _end is ok, missing a _begin is never ok. > Well doesnt the requirement of just one execution thread also deal with > that issue? Yes, except again it can't work for try_to_unmap_cluster. This solution is only applicable to #v10 if I fix try_to_unmap_cluster to only call invalidate_page (relaying on the fact the VM holds a pin and a lock on any page that is being mmu-notifier-invalidated). You can't use the single threaded approach to solve either 1 or 2, because your _begin call is called anywhere and that's where you call the secondary-tlb flush and it's fatal to miss it. invalidate_page is called always after, so it enforced the tlb flush to be called _after_ and so it's inherently safe. ------------------------------------------------------------------------- Check out the new SourceForge.net Marketplace. It's the best place to buy or sell services for just about anything Open Source. http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
