drm/xe/guc: rework exec queue teardown PM/unplug handling

The core_hotunplug "with-load" subtests trigger a "Missing outer runtime
PM protection" warning when an exec queue is torn down from a deferred fd
close after the device has been hot-unplugged:

  guc_exec_queue_add_msg
  guc_exec_queue_destroy
  xe_exec_queue_destroy
  xe_file_close

The reference is not actually missing. On unplug the PCI core disables
runtime PM (device_del() -> __pm_runtime_disable()) while the old
drm_device is kept alive by the still-open fd. Once runtime PM is
disabled pm_runtime_get_if_in_use() returns -EINVAL regardless of the
usage count, so xe_pm_runtime_get_noresume() can no longer observe the
held reference and warns.

drm_dev_unplug() always runs before runtime PM is disabled, so gate the
message submission layer on the bound state instead of the PM reference:

 - guc_exec_queue_add_msg(): only take the noresume PM reference while
   drm_dev_enter() succeeds and record it in the message (MSG_PM_REF), so
   the put in guc_exec_queue_process_msg() stays balanced.

 - guc_exec_queue_process_msg(): re-check the bound state and skip each
   handler's HW access once the device is gone.

 - guc_exec_queue_destroy(): always post the CLEANUP message; the cleanup
   handler issues the deregister H2G only while bound, registered, fw
   running and not wedged, otherwise it tears down on the driver side.

Also document the post-unplug PM-reference hazard in
xe_pm_runtime_get_noresume().

Observed with new IGT core_hotunplug subtests:
  igt@core_hotunplug@hotreplug-with-load
  igt@core_hotunplug@hotunplug-rescan-with-load

v2:
 - Drop the drm_dev_is_unplugged() bypass from guc_exec_queue_destroy()
   and instead exclude hot-unplug from the WARN in
   xe_pm_runtime_get_noresume().

v3:
 - Rework the fix in the message-submission layer instead of touching the
   WARN; gate PM/HW work on drm_dev_enter() and route all queues through
   the CLEANUP message. (Matthew Brost)
 - Prove the root cause (runtime PM disabled on unplug, not a zero
   refcount) and record it in the commit message. (Matt B, Raag)
 - Also remove EXEC_QUEUE_FLAG_PERMANENT flag in
   separate patch (Matthew Brost)

Link: https://patchwork.freedesktop.org/patch/725773/?series=166744&rev=4
Suggested-by: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Raag Jadav <raag.jadav@intel.com>
Signed-off-by: Nitin Gote <nitin.r.gote@intel.com>
Reviewed-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
Tested-by: Varun Gupta <varun.gupta@intel.com>
Link: https://patch.msgid.link/20260811133753.1742666-5-nitin.r.gote@intel.com
Signed-off-by: Tejas Upadhyay <tejas.upadhyay@intel.com>

0 files changed, 0 insertions, 0 deletions