Changes V1->V2: * Rebase to v3.16-rc7 * Added call of ->invalidate_range to __mmu_notifier_invalidate_end() so that the subsystem doesn't need to register an ->invalidate_end() call-back, subsystems will likely either register invalidate_range_start/end or invalidate_range, so that should be fine. * Re-orded declarations a bit to reflect that invalidate_range is not only called between invalidate_range_start/end * Updated documentation to cover the case where invalidate_range is called outside of invalidate_range_start/end to flush page-table pages out of the TLB 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. Furthermore the _start()/end() notifiers only catch the moment when page mappings are released, but not page-table pages. But this is necessary for managing external TLBs when the page-table is shared with the CPU. 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 | 75 +++++++++++++++++++++++++++++++++++++++++--- 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 | 25 +++++++++++++++ mm/rmap.c | 2 +- 10 files changed, 115 insertions(+), 17 deletions(-) -- 1.9.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
