[PATCH v3 0/2] drm/amdkfd: Unmap SVM range from GPU set to no-access

Setting KFD_IOCTL_SVM_ATTR_NO_ACCESS on a GPU used to do nothing: the
range stayed mapped, so the MMU notifier kept evicting GPU queues on CPU
page faults even though the app wanted no access from that GPU.

Patch 1 adds a helper to update the fault checkpoint timestamp and makes
the timestamp atomic so the page fault handler can read it locklessly.

Patch 2 unmaps the range from each GPU set to no-access. Once no GPU maps
the range, the MMU notifier skips queue eviction. It bumps the checkpoint
timestamp so retry faults queued before the unmap are dropped.

v3:
 - Patch 1: fix checkpoint_ts atomic double-read race
 - Patch 2: move checkpoint timestamp update into svm_range_needs_unmap

Philip Yang (2):
  drm/amdkfd: Add helper svm_range_update_checkpoint_timestamp
  drm/amdkfd: Unmap svm range from GPU set to no-access

 drivers/gpu/drm/amd/amdkfd/kfd_priv.h  |   2 +-
 drivers/gpu/drm/amd/amdkfd/kfd_queue.c |   5 +-
 drivers/gpu/drm/amd/amdkfd/kfd_svm.c   | 191 +++++++++++++++----------
 drivers/gpu/drm/amd/amdkfd/kfd_svm.h   |   7 +-
 4 files changed, 126 insertions(+), 79 deletions(-)

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2.50.1