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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. 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 multi-pass in the core appears to be the right choice. Implement two-pass capability in the mmu_interval_notifier. Use a linked list for the final passes to minimize the impact for use-cases that don't need the multi-pass functionality by avoiding a second interval tree walk, and to be able to easily pass data between the two passes. v1: - Restrict to two passes (Jason Gunthorpe) - Improve on documentation (Jason Gunthorpe) - Improve on function naming (Alistair Popple) v2: - Include the invalidate_finish() callback in the struct mmu_interval_notifier_ops. - Update documentation (GitHub Copilot:claude-sonnet-4.6) - Use lockless list for list management. v3: - Update kerneldoc for the struct mmu_interval_notifier_finish::list member (Matthew Brost) - Add a WARN_ON_ONCE() checking for NULL invalidate_finish() op if if invalidate_start() is non-NULL. (Matthew Brost) v4: - Addressed documentation review comments by 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> Assisted-by: GitHub Copilot:claude-sonnet-4.6 # Documentation only. Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> Acked-by: David Hildenbrand (Arm) <david@kernel.org> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Link: https://patch.msgid.link/20260305093909.43623-2-thomas.hellstrom@linux.intel.com