[PATCH v5 0/9] mmu notifier provide context informations

[jglisse]

From: JÃrÃme Glisse <jglisse@xxxxxxxxxx>

Since last version [4] i added the extra bits needed for the change_pte
optimization (which is a KSM thing). Here i am not posting users of
this, they will be posted to the appropriate sub-systems (KVM, GPU,
RDMA, ...) once this serie get upstream. If you want to look at users
of this see [5] [6]. If this gets in 5.1 then i will be submitting
those users for 5.2 (including KVM if KVM folks feel comfortable with
it).

Note that this serie does not change any behavior for any existing
code. It just pass down more informations to mmu notifier listener.

The rational for this patchset:


CPU page table update can happens for many reasons, not only as a
result of a syscall (munmap(), mprotect(), mremap(), madvise(), ...)
but also as a result of kernel activities (memory compression, reclaim,
migration, ...).

This patch introduce a set of enums that can be associated with each
of the events triggering a mmu notifier:

    - UNMAP: munmap() or mremap()
    - CLEAR: page table is cleared (migration, compaction, reclaim, ...)
    - PROTECTION_VMA: change in access protections for the range
    - PROTECTION_PAGE: change in access protections for page in the range
    - SOFT_DIRTY: soft dirtyness tracking

Being able to identify munmap() and mremap() from other reasons why the
page table is cleared is important to allow user of mmu notifier to
update their own internal tracking structure accordingly (on munmap or
mremap it is not longer needed to track range of virtual address as it
becomes invalid). Without this serie, driver are force to assume that
every notification is an munmap which triggers useless trashing within
drivers that associate structure with range of virtual address. Each
driver is force to free up its tracking structure and then restore it
on next device page fault. With this serie we can also optimize device
page table update [5].

More over this can also be use to optimize out some page table updates
like for KVM where we can update the secondary MMU directly from the
callback instead of clearing it.

Patches to leverage this serie will be posted separately to each sub-
system.

Cheers,
JÃrÃme

[1] v1 https://lkml.org/lkml/2018/3/23/1049
[2] v2 https://lkml.org/lkml/2018/12/5/10
[3] v3 https://lkml.org/lkml/2018/12/13/620
[4] v4 https://lkml.org/lkml/2019/1/23/838
[5] patches to use this:
    https://lkml.org/lkml/2019/1/23/833
    https://lkml.org/lkml/2019/1/23/834
    https://lkml.org/lkml/2019/1/23/832
    https://lkml.org/lkml/2019/1/23/831
[6] KVM restore change pte optimization
    https://patchwork.kernel.org/cover/10791179/

Cc: Christian KÃnig <christian.koenig@xxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Felix Kuehling <Felix.Kuehling@xxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Ross Zwisler <zwisler@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Christian Koenig <christian.koenig@xxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: linux-rdma@xxxxxxxxxxxxxxx
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: Arnd Bergmann <arnd@xxxxxxxx>

JÃrÃme Glisse (9):
  mm/mmu_notifier: helper to test if a range invalidation is blockable
  mm/mmu_notifier: convert user range->blockable to helper function
  mm/mmu_notifier: convert mmu_notifier_range->blockable to a flags
  mm/mmu_notifier: contextual information for event enums
  mm/mmu_notifier: contextual information for event triggering
    invalidation v2
  mm/mmu_notifier: use correct mmu_notifier events for each invalidation
  mm/mmu_notifier: pass down vma and reasons why mmu notifier is
    happening v2
  mm/mmu_notifier: mmu_notifier_range_update_to_read_only() helper
  mm/mmu_notifier: set MMU_NOTIFIER_USE_CHANGE_PTE flag where
    appropriate v2

 drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c  |  8 +--
 drivers/gpu/drm/i915/i915_gem_userptr.c |  2 +-
 drivers/gpu/drm/radeon/radeon_mn.c      |  4 +-
 drivers/infiniband/core/umem_odp.c      |  5 +-
 drivers/xen/gntdev.c                    |  6 +-
 fs/proc/task_mmu.c                      |  3 +-
 include/linux/mmu_notifier.h            | 93 +++++++++++++++++++++++--
 kernel/events/uprobes.c                 |  3 +-
 mm/hmm.c                                |  6 +-
 mm/huge_memory.c                        | 14 ++--
 mm/hugetlb.c                            | 12 ++--
 mm/khugepaged.c                         |  3 +-
 mm/ksm.c                                |  9 ++-
 mm/madvise.c                            |  3 +-
 mm/memory.c                             | 26 ++++---
 mm/migrate.c                            |  5 +-
 mm/mmu_notifier.c                       | 12 +++-
 mm/mprotect.c                           |  4 +-
 mm/mremap.c                             |  3 +-
 mm/oom_kill.c                           |  3 +-
 mm/rmap.c                               |  6 +-
 virt/kvm/kvm_main.c                     |  3 +-
 22 files changed, 180 insertions(+), 53 deletions(-)

-- 
2.17.2