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SubjectRe: [PATCH v3 hmm 00/11] Add mmu_notifier_get/put for managing mmu notifier registrations
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On 8/6/19 4:15 PM, Jason Gunthorpe wrote:
> From: Jason Gunthorpe <jgg@mellanox.com>
>
> This series introduces a new registration flow for mmu_notifiers based on
> the idea that the user would like to get a single refcounted piece of
> memory for a mm, keyed to its use.
>
> For instance many users of mmu_notifiers use an interval tree or similar
> to dispatch notifications to some object. There are many objects but only
> one notifier subscription per mm holding the tree.
>
> Of the 12 places that call mmu_notifier_register:
> - 7 are maintaining some kind of obvious mapping of mm_struct to
> mmu_notifier registration, ie in some linked list or hash table. Of
> the 7 this series converts 4 (gru, hmm, RDMA, radeon)
>
> - 3 (hfi1, gntdev, vhost) are registering multiple notifiers, but each
> one immediately does some VA range filtering, ie with an interval tree.
> These would be better with a global subsystem-wide range filter and
> could convert to this API.
>
> - 2 (kvm, amd_iommu) are deliberately using a single mm at a time, and
> really can't use this API. One of the intel-svm's modes is also in this
> list
>
> The 3/7 unconverted drivers are:
> - intel-svm
> This driver tracks mm's in a global linked list 'global_svm_list'
> and would benefit from this API.
>
> Its flow is a bit complex, since it also wants a set of non-shared
> notifiers.
>
> - i915_gem_usrptr
> This driver tracks mm's in a per-device hash
> table (dev_priv->mm_structs), but only has an optional use of
> mmu_notifiers. Since it still seems to need the hash table it is
> difficult to convert.
>
> - amdkfd/kfd_process
> This driver is using a global SRCU hash table to track mm's
>
> The control flow here is very complicated and the driver is relying on
> this hash table to be fast on the ioctl syscall path.
>
> It would definitely benefit, but only if the ioctl path didn't need to
> do the search so often.
>
> This series is already entangled with patches in the hmm & RDMA tree and
> will require some git topic branches for the RDMA ODP stuff. I intend for
> it to go through the hmm tree.
>
> There is a git version here:
>
> https://github.com/jgunthorpe/linux/commits/mmu_notifier
>
> Which has the required pre-patches for the RDMA ODP conversion that are
> still being reviewed.
>
> Jason Gunthorpe (11):
> mm/mmu_notifiers: hoist do_mmu_notifier_register down_write to the
> caller
> mm/mmu_notifiers: do not speculatively allocate a mmu_notifier_mm
> mm/mmu_notifiers: add a get/put scheme for the registration
> misc/sgi-gru: use mmu_notifier_get/put for struct gru_mm_struct
> hmm: use mmu_notifier_get/put for 'struct hmm'
> RDMA/odp: use mmu_notifier_get/put for 'struct ib_ucontext_per_mm'
> RDMA/odp: remove ib_ucontext from ib_umem
> drm/radeon: use mmu_notifier_get/put for struct radeon_mn
> drm/amdkfd: fix a use after free race with mmu_notifer unregister
> drm/amdkfd: use mmu_notifier_put
> mm/mmu_notifiers: remove unregister_no_release
>
> drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c | 1 +
> drivers/gpu/drm/amd/amdkfd/kfd_priv.h | 3 -
> drivers/gpu/drm/amd/amdkfd/kfd_process.c | 88 ++++-----
> drivers/gpu/drm/nouveau/nouveau_drm.c | 3 +
> drivers/gpu/drm/radeon/radeon.h | 3 -
> drivers/gpu/drm/radeon/radeon_device.c | 2 -
> drivers/gpu/drm/radeon/radeon_drv.c | 2 +
> drivers/gpu/drm/radeon/radeon_mn.c | 157 ++++------------
> drivers/infiniband/core/umem.c | 4 +-
> drivers/infiniband/core/umem_odp.c | 183 ++++++------------
> drivers/infiniband/core/uverbs_cmd.c | 3 -
> drivers/infiniband/core/uverbs_main.c | 1 +
> drivers/infiniband/hw/mlx5/main.c | 5 -
> drivers/misc/sgi-gru/grufile.c | 1 +
> drivers/misc/sgi-gru/grutables.h | 2 -
> drivers/misc/sgi-gru/grutlbpurge.c | 84 +++------
> include/linux/hmm.h | 12 +-
> include/linux/mm_types.h | 6 -
> include/linux/mmu_notifier.h | 40 +++-
> include/rdma/ib_umem.h | 2 +-
> include/rdma/ib_umem_odp.h | 10 +-
> include/rdma/ib_verbs.h | 3 -
> kernel/fork.c | 1 -
> mm/hmm.c | 121 +++---------
> mm/mmu_notifier.c | 230 +++++++++++++++++------
> 25 files changed, 408 insertions(+), 559 deletions(-)

For the core MM, HMM, and nouveau changes you can add:
Tested-by: Ralph Campbell <rcampbell@nvidia.com>

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