From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jerome Glisse Subject: Re: [PATCH 1/3] mmu_notifier: Add mmu_notifier_invalidate_range() Date: Fri, 25 Jul 2014 16:43:15 -0400 Message-ID: <20140725204314.GA5478@gmail.com> References: <1406212541-25975-1-git-send-email-joro@8bytes.org> <1406212541-25975-2-git-send-email-joro@8bytes.org> <20140725131639.698f18ff@jbarnes-desktop> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <20140725131639.698f18ff@jbarnes-desktop> Sender: owner-linux-mm@kvack.org To: Jesse Barnes Cc: Joerg Roedel , Andrew Morton , Andrea Arcangeli , Peter Zijlstra , Rik van Riel , Hugh Dickins , Mel Gorman , Johannes Weiner , Jerome Glisse , jroedel@suse.de, Jay.Cornwall@amd.com, Oded.Gabbay@amd.com, John.Bridgman@amd.com, Suravee.Suthikulpanit@amd.com, ben.sander@amd.com, David Woodhouse , linux-kernel@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org List-Id: iommu@lists.linux-foundation.org On Fri, Jul 25, 2014 at 01:16:39PM -0700, Jesse Barnes wrote: > On Thu, 24 Jul 2014 16:35:39 +0200 > Joerg Roedel wrote: >=20 > > From: Joerg Roedel > >=20 > > This notifier closes an important gap with the current > > invalidate_range_start()/end() notifiers. The _start() part > > is called when all pages are still mapped while the _end() > > notifier is called when all pages are potentially unmapped > > and already freed. > >=20 > > This does not allow to manage external (non-CPU) hardware > > TLBs with MMU-notifiers because there is no way to prevent > > that hardware will establish new TLB entries between the > > calls of these two functions. But this is a requirement to > > the subsytem that implements these existing notifiers. > >=20 > > To allow managing external TLBs the MMU-notifiers need to > > catch the moment when pages are unmapped but not yet freed. > > This new notifier catches that moment and notifies the > > interested subsytem when pages that were unmapped are about > > to be freed. The new notifier will only be called between > > invalidate_range_start()/end(). >=20 > So if we were actually sharing page tables, we should be able to make > start/end no-ops and just use this new callback, assuming we didn't > need to do any other serialization or debug stuff, right? >=20 > Seems like a good addition, and saves us a bunch of trouble... Pondering on that i think there is a missing call to mmu_notifier_invalid= ate_range inside move_huge_pmd which is call by move_page_tables.=20 But otherwise yes, you should not need to register range_start/end() call= back. It should be enought to only register the invalidate_range callback. Note that on my side i will remain an user of range_start/end() but other= listener like kvm or xen or sgi might want to revisit there code with this new cal= lback. Cheers, J=E9r=F4me >=20 > Thanks, > --=20 > Jesse Barnes, Intel Open Source Technology Center >=20 > -- > 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 -- 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