[Bug 103800] CNL unable to handle kernel paging request at 00000000fffffffc
bugzilla-daemon at freedesktop.org
bugzilla-daemon at freedesktop.org
Wed Nov 29 00:35:50 UTC 2017
https://bugs.freedesktop.org/show_bug.cgi?id=103800
Chris Wilson <chris at chris-wilson.co.uk> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |WORKSFORME
--- Comment #16 from Chris Wilson <chris at chris-wilson.co.uk> ---
No worries then, we'll just assume that it was fixed by
commit ba74cb10c775c839f6e1d0fabd1e772eabd9c43f
Author: Michel Thierry <michel.thierry at intel.com>
Date: Mon Nov 20 12:34:58 2017 +0000
drm/i915/execlists: Delay writing to ELSP until HW has processed the
previous write
The hardware needs some time to process the information received in the
ExecList Submission Port, and expects us to not write anything more until
it has 'acknowledged' this new submission by sending an IDLE_ACTIVE or
PREEMPTED CSB event.
If we do not follow this, the driver could write new data into the ELSP
before HW had finishing fetching the previous one, putting us in
'undefined behaviour' space.
This seems to be the problem causing the spurious PREEMPTED & COMPLETE
events after a COMPLETE like the one below:
[] vcs0: sw rd pointer = 2, hw wr pointer = 0, current 'head' = 3.
[] vcs0: Execlist CSB[0]: 0x00000018 _ 0x00000007
[] vcs0: Execlist CSB[1]: 0x00000001 _ 0x00000000
[] vcs0: Execlist CSB[2]: 0x00000018 _ 0x00000007 <<< COMPLETE
[] vcs0: Execlist CSB[3]: 0x00000012 _ 0x00000007 <<< PREEMPTED &
COMPLETE
[] vcs0: Execlist CSB[4]: 0x00008002 _ 0x00000006
[] vcs0: Execlist CSB[5]: 0x00000014 _ 0x00000006
The ELSP writes that lead to this CSB sequence show that the HW hadn't
started executing the previous execlist (the one with only ctx 0x6) by the
time the new one was submitted; this is a bit more clear in the data
show in the EXECLIST_STATUS register at the time of the ELSP write.
[] vcs0: ELSP[0] = 0x0_0 [execlist1] - status_reg = 0x0_302
[] vcs0: ELSP[1] = 0x6_fedb2119 [execlist0] - status_reg = 0x0_8302
[] vcs0: ELSP[2] = 0x7_fedaf119 [execlist1] - status_reg = 0x0_8308
[] vcs0: ELSP[3] = 0x6_fedb2119 [execlist0] - status_reg = 0x7_8308
Note that having to wait for this ack does not disable lite-restores,
although it may reduce their numbers.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102035
Signed-off-by: Michel Thierry <michel.thierry at intel.com>
Link:
https://patchwork.freedesktop.org/patch/msgid/<20171118003038.7935-1-michel.thierry@intel.com>
Link:
https://patchwork.freedesktop.org/patch/msgid/20171120123458.23242-4-chris@chris-wilson.co.uk
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
Tested-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
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