From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 21 Feb 2008 05:47:04 +0100 From: Nick Piggin Subject: Re: [patch] my mmu notifiers Message-ID: <20080221044704.GB15215@wotan.suse.de> References: <20080219084357.GA22249@wotan.suse.de> <20080219135851.GI7128@v2.random> <20080219231157.GC18912@wotan.suse.de> <20080220010941.GR7128@v2.random> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080220010941.GR7128@v2.random> Sender: owner-linux-mm@kvack.org Return-Path: To: Andrea Arcangeli Cc: akpm@linux-foundation.org, Robin Holt , Avi Kivity , Izik Eidus , kvm-devel@lists.sourceforge.net, Peter Zijlstra , general@lists.openfabrics.org, Steve Wise , Roland Dreier , Kanoj Sarcar , steiner@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, daniel.blueman@quadrics.com, Christoph Lameter List-ID: On Wed, Feb 20, 2008 at 02:09:41AM +0100, Andrea Arcangeli wrote: > On Wed, Feb 20, 2008 at 12:11:57AM +0100, Nick Piggin wrote: > > Sorry, I realise I still didn't get this through my head yet (and also > > have not seen your patch recently). So I don't know exactly what you > > are doing... > > The last version was posted here: > > http://marc.info/?l=kvm-devel&m=120321732521533&w=2 > > > But why does _anybody_ (why does Christoph's patches) need to invalidate > > when they are going to be more permissive? This should be done lazily by > > the driver, I would have thought. > > This can be done lazily by the driver yes. The place where I've an > invalidate_pages in mprotect however can also become less permissive. That's OK, because we have to flush tlbs there too. > It's simpler to invalidate always and it's not guaranteed the > secondary mmu page fault is capable of refreshing the spte across a > writeprotect fault. I think we just have to make sure that it _can_ do writeprotect faults. AFAIKS, that will be possible if the driver registers a .page_mkwrite handler (actually not quite -- page_mkwrite is fairly crap, so I have a patch to merge it together with .fault so we get address information as well). Anyway, I really think we should do it that way. > In the future this can be changed to > mprotect_pages though, so no page fault will happen in the secondary > mmu. Possibly, but hopefully not needed for performance. Let's wait and see. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org