From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: [PATCH 0/3] mmu_notifier: Allow to manage CPU external TLBs Date: Thu, 24 Jul 2014 16:35:38 +0200 Message-ID: <1406212541-25975-1-git-send-email-joro@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Andrew Morton , Andrea Arcangeli , Peter Zijlstra , Rik van Riel , Hugh Dickins , Mel Gorman , Johannes Weiner Cc: Jay.Cornwall-5C7GfCeVMHo@public.gmane.org, John.Bridgman-5C7GfCeVMHo@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, Jerome Glisse , jroedel-l3A5Bk7waGM@public.gmane.org, Jesse Barnes , David Woodhouse , ben.sander-5C7GfCeVMHo@public.gmane.org List-Id: iommu@lists.linux-foundation.org Hi, here is a patch-set to extend the mmu_notifiers in the Linux kernel to allow managing CPU external TLBs. Those TLBs may be implemented in IOMMUs or any other external device, e.g. ATS/PRI capable PCI devices. The problem with managing these TLBs are the semantics of the invalidate_range_start/end call-backs currently available. Currently the subsystem using mmu_notifiers has to guarantee that no new TLB entries are established between invalidate_range_start/end. Furthermore the invalidate_range_start() function is called when all pages are still mapped and invalidate_range_end() when the pages are unmapped an already freed. So both call-backs can't be used to safely flush any non-CPU TLB because _start() is called too early and _end() too late. In the AMD IOMMUv2 driver this is currently implemented by assigning an empty page-table to the external device between _start() and _end(). But as tests have shown this doesn't work as external devices don't re-fault infinitly but enter a failure state after some time. Next problem with this solution is that it causes an interrupt storm for IO page faults to be handled when an empty page-table is assigned. To solve this situation I wrote a patch-set to introduce a new notifier call-back: mmu_notifer_invalidate_range(). This notifier lifts the strict requirements that no new references are taken in the range between _start() and _end(). When the subsystem can't guarantee that any new references are taken is has to provide the invalidate_range() call-back to clear any new references in there. It is called between invalidate_range_start() and _end() every time the VMM has to wipe out any references to a couple of pages. This are usually the places where the CPU TLBs are flushed too and where its important that this happens before invalidate_range_end() is called. Any comments and review appreciated! Thanks, Joerg Joerg Roedel (3): mmu_notifier: Add mmu_notifier_invalidate_range() mmu_notifier: Call mmu_notifier_invalidate_range() from VMM mmu_notifier: Add the call-back for mmu_notifier_invalidate_range() include/linux/mmu_notifier.h | 66 ++++++++++++++++++++++++++++++++++++++++---- kernel/events/uprobes.c | 2 +- mm/fremap.c | 2 +- mm/huge_memory.c | 9 +++--- mm/hugetlb.c | 7 ++++- mm/ksm.c | 4 +-- mm/memory.c | 3 +- mm/migrate.c | 3 +- mm/mmu_notifier.c | 15 ++++++++++ mm/rmap.c | 2 +- 10 files changed, 95 insertions(+), 18 deletions(-) -- 1.9.1