From: Tvrtko Ursulin tvrtko.ursulin@intel.com
commit dc3421560a67361442f33ec962fc6dd48895a0df upstream.
When considering whether to mark one context as stopped and another as started we need to look at whether the previous and new _contexts_ are different and not just requests. Otherwise the software tracked context start time was incorrectly updated to the most recent lite-restore time- stamp, which was in some cases resulting in active time going backward, until the context switch (typically the heartbeat pulse) would synchronise with the hardware tracked context runtime. Easiest use case to observe this behaviour was with a full screen clients with close to 100% engine load.
Signed-off-by: Tvrtko Ursulin tvrtko.ursulin@intel.com Fixes: bb6287cb1886 ("drm/i915: Track context current active time") Cc: stable@vger.kernel.org # v5.19+ Reviewed-by: Matthew Auld matthew.auld@intel.com Link: https://patchwork.freedesktop.org/patch/msgid/20230320151423.1708436-1-tvrtk... [tursulin: Fix spelling in commit msg.] (cherry picked from commit b3e70051879c665acdd3a1ab50d0ed58d6a8001f) Signed-off-by: Jani Nikula jani.nikula@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/i915/gt/intel_execlists_submission.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
--- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c @@ -2017,6 +2017,8 @@ process_csb(struct intel_engine_cs *engi * inspecting the queue to see if we need to resumbit. */ if (*prev != *execlists->active) { /* elide lite-restores */ + struct intel_context *prev_ce = NULL, *active_ce = NULL; + /* * Note the inherent discrepancy between the HW runtime, * recorded as part of the context switch, and the CPU @@ -2028,9 +2030,15 @@ process_csb(struct intel_engine_cs *engi * and correct overselves later when updating from HW. */ if (*prev) - lrc_runtime_stop((*prev)->context); + prev_ce = (*prev)->context; if (*execlists->active) - lrc_runtime_start((*execlists->active)->context); + active_ce = (*execlists->active)->context; + if (prev_ce != active_ce) { + if (prev_ce) + lrc_runtime_stop(prev_ce); + if (active_ce) + lrc_runtime_start(active_ce); + } new_timeslice(execlists); }