We now have proper infrastructure to accurately check the LRC timestamp
without toggling the scheduling state for non-VFs. For VFs, it is still
possible to get an inaccurate view if the context is on hardware. We
guard against free-running contexts on VFs by banning jobs whose
timestamps are not moving. In addition, VFs have a timeslice quantum
that naturally triggers context switches when more than one VF is
running, thus updating the LRC timestamp.
For multi-queue, it is desirable to avoid scheduling toggling in the TDR
because this scheduling state is shared among many queues. Furthermore,
this change simplifies the GuC state machine. The trade-off for VF cases
seems worthwhile.
v5:
- Add xe_lrc_timestamp helper (Umesh)
v6:
- Reduce number of tries on stuck timestamp (VF testing)
- Convert job timestamp save to a memory copy (VF testing)
v7:
- Save ctx timestamp to LRC when start VF job (VF testing)
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Link: https://patch.msgid.link/20260110012739.2888434-8-matthew.brost@intel.com
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