Re: [PATCH v5 0/9] drm/xe/madvise: Add support for purgeable buffer objects

["Yadav, Arvind" <arvind.yadav@intel.com>]

On 11-02-2026 21:16, Matthew Brost wrote:
> On Wed, Feb 11, 2026 at 08:56:29PM +0530, Arvind Yadav wrote:
>
> I have a feeling from the KMD POV we are getting close for this being
> ready to merge. What is the status a UMD PR to use this feature (?) as
> this is a prerequisite to merging.
>
> Also it likely time to start collecting ack's from the UMD teams on the
> the uAPI patch too.

Hi Jose,

Since this is now close to merge. Can you or some from UMD side to Ack 
the uAPI patch.

Thanks,
Arvind

>
> Matt
>
>> This patch series introduces comprehensive support for purgeable buffer objects
>> in the Xe driver, enabling userspace to provide memory usage hints for better
>> memory management under system pressure.
>>
>> Overview:
>>
>> Purgeable memory allows applications to mark buffer objects as "not currently
>> needed" (DONTNEED), making them eligible for kernel reclamation during memory
>> pressure. This helps prevent OOM conditions and enables more efficient GPU
>> memory utilization for workloads with temporary or regeneratable data (caches,
>> intermediate results, decoded frames, etc.).
>>
>> Purgeable BO Lifecycle:
>> 1. WILLNEED (default): BO actively needed, kernel preserves backing store
>> 2. DONTNEED (user hint): BO contents discardable, eligible for purging
>> 3. PURGED (kernel action): Backing store reclaimed during memory pressure
>>
>> Key Design Principles:
>>    - i915 compatibility: "Once purged, always purged" semantics - purged BOs
>>      remain permanently invalid and must be destroyed/recreated
>>    - Per-VMA state tracking: Each VMA tracks its own purgeable state, BO is
>>      only marked DONTNEED when ALL VMAs across ALL VMs agree (Thomas Hellström)
>>    - Safety first: Imported/exported dma-bufs blocked from purgeable state -
>>      no visibility into external device usage (Matt Roper)
>>    - Multiple protection layers: Validation in madvise, VM bind, mmap, and
>>      fault handlers
>>    - Async TLB invalidation: Uses xe_bo_trigger_rebind() for non-blocking
>>      GPU mapping invalidation
>>    - Scratch PTE support: Fault-mode VMs use scratch pages for safe zero reads
>>      on purged BO access.
>>    - Purgeable state is not applied to imported/exported dma-bufs,
>>      those BOs always behave as WILLNEED.
>>    - TTM shrinker integration: Encapsulated helpers manage xe_ttm_tt->purgeable
>>      flag and shrinker page accounting (shrinkable vs purgeable buckets)
>>
>> v2 Changes:
>>    - Reordered patches: Moved shared BO helper before main implementation for
>>      proper dependency order
>>    - Fixed reference counting in mmap offset validation (use drm_gem_object_put)
>>    - Removed incorrect claims about madvise(WILLNEED) restoring purged BOs
>>    - Fixed error code documentation inconsistencies
>>    - Initialize purge_state_val fields to prevent kernel memory leaks
>>    - Use xe_bo_trigger_rebind() for async TLB invalidation (Thomas Hellström)
>>    - Add NULL rebind with scratch PTEs for fault mode (Thomas Hellström)
>>    - Implement i915-compatible retained field logic (Thomas Hellström)
>>    - Skip BO validation for purged BOs in page fault handler (crash fix)
>>    - Add scratch VM check in page fault path (non-scratch VMs fail fault)
>>
>> v3 Changes (addressing Matt and Thomas Hellström feedback):
>>    - Per-VMA purgeable state tracking: Added xe_vma->purgeable_state field
>>    - Complete VMA check: xe_bo_all_vmas_dontneed() walks all VMAs across all
>>      VMs to ensure unanimous DONTNEED before marking BO purgeable
>>    - VMA unbind recheck: Added xe_bo_recheck_purgeable_on_vma_unbind() to
>>      re-evaluate BO state when VMAs are destroyed
>>    - Block external dma-bufs: Added xe_bo_is_external_dmabuf() check using
>>      drm_gem_is_imported() and obj->dma_buf to prevent purging imported/exported BOs
>>    - Consistent lockdep enforcement: Added xe_bo_assert_held() to all helpers
>>      that access madv_purgeable state
>>    - Simplified page table logic: Renamed is_null to is_null_or_purged in
>>      xe_pt_stage_bind_entry() - purged BOs treated identically to null VMAs
>>    - Removed unnecessary checks: Dropped redundant "&& bo" check in xe_ttm_bo_purge()
>>    - Xe-specific warnings: Changed drm_warn() to XE_WARN_ON() in purge path
>>    - Moved purge checks under locks: Purge state validation now done after
>>      acquiring dma-resv lock in vma_lock_and_validate() and xe_pagefault_begin()
>>    - Race-free fault handling: Removed unlocked purge check from
>>      xe_pagefault_handle_vma(), moved to locked xe_pagefault_begin()
>>    - Shrinker helper functions: Added xe_bo_set_purgeable_shrinker() and
>>      xe_bo_clear_purgeable_shrinker() to encapsulate TTM purgeable flag updates
>>      and shrinker page accounting, improving code clarity and maintainability
>>
>> v4 Changes (addressing Matt and Thomas Hellström feedback):
>>    - UAPI: Removed '__u64 reserved' field from purge_state_val union to fit
>>      16-byte size constraint (Matt)
>>    - Changed madv_purgeable from atomic_t to u32 across all patches (Matt)
>>    - CPU fault handling: Added purged check to fastpath (xe_bo_cpu_fault_fastpath)
>>      to prevent hang when accessing existing mmap of purged BO
>>
>> v5 Changes (addressing Matt and Thomas Hellström feedback):
>>    - Add locking documentation to madv_purgeable field comment (Matt)
>>    - Introduce xe_bo_set_purgeable_state() helper (void return) to centralize
>>      madv_purgeable updates with xe_bo_assert_held() and state transition
>>      validation using explicit enum checks (no transition out of PURGED) (Matt)
>>    - Make xe_ttm_bo_purge() return int and propagate failures from
>>      xe_bo_move(); handle xe_bo_trigger_rebind() failures (e.g. no_wait_gpu
>>      paths) rather than silently ignoring (Matt)
>>    - Replace drm_WARN_ON with xe_assert for better Xe-specific assertions (Matt)
>>    - Hook purgeable handling into madvise_funcs[DRM_XE_VMA_ATTR_PURGEABLE_STATE]
>>      instead of special-case path in xe_vm_madvise_ioctl() (Matt)
>>    - Track purgeable retained return via xe_madvise_details and perform
>>      copy_to_user() from xe_madvise_details_fini() after locks are dropped (Matt)
>>    - Set madvise_funcs[DRM_XE_VMA_ATTR_PURGEABLE_STATE] to NULL with
>>      __maybe_unused on madvise_purgeable() to maintain bisectability until
>>      shrinker integration is complete in final patch (Matt)
>>    - Call xe_bo_recheck_purgeable_on_vma_unbind() from xe_vma_destroy()
>>      right after drm_gpuva_unlink() where we already hold the BO lock,
>>      drop the trylock-based late destroy path (Matt)
>>    - Move purgeable_state into xe_vma_mem_attr with the other madvise
>>      attributes (Matt)
>>    - Drop READ_ONCE since the BO lock already protects us (Matt)
>>    - Keep returning false when there are no VMAs - otherwise we'd mark
>>      BOs purgeable without any user hint (Matt)
>>    -  Use struct xe_vma_lock_and_validate_flags instead of multiple bool
>>      parameters to improve readability and prevent argument transposition (Matt)
>>    - Fix LRU crash while running shrink test
>>    - Skip xe_bo_validate() for purged BOs in xe_gpuvm_validate()
>>    - Split ghost BO and zero-refcount handling in xe_bo_shrink() (Thomas)
>>
>> Arvind Yadav (8):
>>    drm/xe/bo: Add purgeable bo state tracking and field madv to xe_bo
>>    drm/xe/madvise: Implement purgeable buffer object support
>>    drm/xe/bo: Handle CPU faults on purged buffer objects
>>    drm/xe/vm: Prevent binding of purged buffer objects
>>    drm/xe/madvise: Implement per-VMA purgeable state tracking
>>    drm/xe/madvise: Block imported and exported dma-bufs
>>    drm/xe/bo: Add purgeable shrinker state helpers
>>    drm/xe/madvise: Enable purgeable buffer object IOCTL support
>>
>> Himal Prasad Ghimiray (1):
>>    drm/xe/uapi: Add UAPI support for purgeable buffer objects
>>
>>   drivers/gpu/drm/xe/xe_bo.c         | 187 ++++++++++++++++++++--
>>   drivers/gpu/drm/xe/xe_bo.h         |  60 +++++++
>>   drivers/gpu/drm/xe/xe_bo_types.h   |   6 +
>>   drivers/gpu/drm/xe/xe_pagefault.c  |  12 ++
>>   drivers/gpu/drm/xe/xe_pt.c         |  40 ++++-
>>   drivers/gpu/drm/xe/xe_vm.c         |  90 +++++++++--
>>   drivers/gpu/drm/xe/xe_vm_madvise.c | 249 +++++++++++++++++++++++++++++
>>   drivers/gpu/drm/xe/xe_vm_madvise.h |   3 +
>>   drivers/gpu/drm/xe/xe_vm_types.h   |  11 ++
>>   include/uapi/drm/xe_drm.h          |  44 +++++
>>   10 files changed, 667 insertions(+), 35 deletions(-)
>>
>> -- 
>> 2.43.0
>>