drm/xe: Fix LR exec queue suspend/resume for S3/S4

Long Running (LR) exec queues — used by compute workloads with SVM (fault-mode) and by preempt-fence-mode — were not surviving S3/S4 suspend/resume correctly. Four distinct problems are addressed:

1. Exec queue ops (guc_exec_queue_suspend/resume) lacked coordination when multiple paths (PM, mode switching, preempt fences) needed to hold the queue suspended simultaneously. A suspend refcount ensures the GuC SUSPEND message is only sent when the first caller suspends, and the RESUME message only when the last caller resumes.

2. During PM suspend, guc_exec_queue_stop() banned any user exec queue that had a started-but-incomplete job. For LR queues this is always true — their jobs are designed to run indefinitely — so every PM suspend permanently banned the queue. The ban is now suppressed for LR VM exec queues during PM suspend or hibernation while being preserved for GT reset (legitimate hang detection).

3. Userspace LRC buffer objects carried XE_BO_FLAG_PINNED_LATE_RESTORE, deferring their VRAM restore to after xe_gt_resume(). However, xe_gt_resume() drives context registration, which requires valid LRC VRAM. Dropping the flag moves the restore to xe_bo_restore_early(), a CPU/BAR copy that runs before xe_gt_resume(), fixing the ordering.

4. Fault-mode (SVM) VMs use GPU page faults to access memory. A running fault-mode job can re-fault pages torn down by VRAM eviction, racing with the eviction. A new xe_suspend_all_faulting_lr_jobs() call in the PM notifier stops all fault-mode queues and waits for GuC acknowledgement before eviction begins. On resume, xe_resume_all_faulting_lr_jobs() mirrors the same iteration to re-register and resume exactly those queues. A per-group pm_suspended flag (protected by mode_sem) prevents new fault-mode exec queues from slipping through unsuspended while PM suspend is in progress.

Note: A prerequisite revert ("Revert drm/xe: Skip exec queue schedule toggle if queue is idle during suspend") was already sent as a separate patch and is not included here.

Thomas Hellström (4):
drm/xe/guc: Add suspend refcount to exec queue ops drm/xe/guc: Don't ban LR VM exec queues on PM suspend drm/xe: Restore userspace LRC BOs early on resume drm/xe: Suspend fault-mode LR jobs before VRAM eviction on S3/S4

 drivers/gpu/drm/xe/xe_exec_queue_types.h      |   7 +
 drivers/gpu/drm/xe/xe_guc_exec_queue_types.h  |   7 +
 drivers/gpu/drm/xe/xe_guc_submit.c            |  60 +++++--
 drivers/gpu/drm/xe/xe_guc_submit.h            |   1 +
 drivers/gpu/drm/xe/xe_hw_engine_group.c       | 158 +++++++++++++++++-
 drivers/gpu/drm/xe/xe_hw_engine_group.h       |   3 +
 drivers/gpu/drm/xe/xe_hw_engine_group_types.h |   7 +
 drivers/gpu/drm/xe/xe_lrc.c                   |   2 +-
 drivers/gpu/drm/xe/xe_pm.c                    |  15 +-
 9 files changed, 239 insertions(+), 21 deletions(-)

2.54.0