GPU use-cases for mmu_interval_notifiers with hmm often involve
starting a gpu operation and then waiting for it to complete.
These operations are typically context preemption or TLB flushing.
    
With single-pass notifiers per GPU this doesn't scale in
multi-gpu scenarios. In those scenarios we'd want to first start
preemption- or TLB flushing on all GPUs and as a second pass wait
for them to complete.

This also applies in non-recoverable page-fault scenarios to
starting a preemption requests on GPUs and waiting for the GPUs 
to preempt so that system pages they access can be reclaimed.
    
One can do this on per-driver basis multiplexing per-driver
notifiers but that would mean sharing the notifier "user" lock
across all GPUs and that doesn't scale well either, so adding support
for two-pass in the core appears like the right choice.

So this series does that, with pach 1 implementing the core support
and also describes the choices made.

The rest of the patches implements a POC with xeKMD userptr
invalidation and potential TLB-flushing. A follow-up series
will extend to drm_gpusvm.

v2 hightlights:
- Refactor the core mm patch to use the struct
  mmu_interval_notifier_ops for the invalidate_finish() callback.
- Rebase on xe driver tlb invalidation changes.
- Provide an initial implementation for userptr instead of drm_gpusvm.
  The intent is to handle drm_gpusvm in a follow-up series.

v3:
- Address review comments from Matt Brost: Code formatting,
  documentation, additional asserts and removal of
  unnecessary waits, as specified in each patch.

v4:
- Extend to wider audience and add R-Bs on the xe patches.
- Address documentation review comments from David Hildenbrand

Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: David Hildenbrand <david@kernel.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Simona Vetter <simona.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@gmail.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: <dri-devel@lists.freedesktop.org>
Cc: <linux-mm@kvack.org>
Cc: <linux-kernel@vger.kernel.org>
    
Thomas Hellström (4):
  mm/mmu_notifier: Allow two-pass struct mmu_interval_notifiers
  drm/xe/userptr: Convert invalidation to two-pass MMU notifier
  drm/xe: Split TLB invalidation into submit and wait steps
  drm/xe/userptr: Defer Waiting for TLB invalidation to the second pass
    if possible

 drivers/gpu/drm/xe/xe_svm.c             |   8 +-
 drivers/gpu/drm/xe/xe_tlb_inval.c       |  84 +++++++++++++
 drivers/gpu/drm/xe/xe_tlb_inval.h       |   6 +
 drivers/gpu/drm/xe/xe_tlb_inval_types.h |  14 +++
 drivers/gpu/drm/xe/xe_userptr.c         | 155 ++++++++++++++++++++----
 drivers/gpu/drm/xe/xe_userptr.h         |  31 ++++-
 drivers/gpu/drm/xe/xe_vm.c              |  99 +++++----------
 drivers/gpu/drm/xe/xe_vm.h              |   5 +-
 drivers/gpu/drm/xe/xe_vm_madvise.c      |  10 +-
 drivers/gpu/drm/xe/xe_vm_types.h        |   1 +
 include/linux/mmu_notifier.h            |  42 +++++++
 mm/mmu_notifier.c                       |  65 ++++++++--
 12 files changed, 416 insertions(+), 104 deletions(-)

-- 
2.53.0