On Tue, 14 Feb 2017, Daniel Vetter <daniel@xxxxxxxx> wrote: > On Tue, Feb 14, 2017 at 02:49:21PM +0200, Jani Nikula wrote: >> From: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx> >> >> 100% reproducible issue found on SKL SkullCanyon NUC with two external >> DP daisy-chained monitors in DP/MST mode. When turning off or changing >> the input of the second monitor the machine stops with a kernel >> oops. This issue happened with 4.8.8 as well as drm/drm-intel-nightly. >> >> This issue is traced to an inconsistent control flow in >> drm_dp_update_payload_part1(): the 'port' pointer is set to NULL at the >> same time as 'req_payload.num_slots' is set to zero, but the pointer is >> dereferenced even when req_payload.num_slot is zero. >> >> The problematic dereference was introduced in commit dfda0df34 >> ("drm/mst: rework payload table allocation to conform better") and may >> impact all versions since v3.18 >> >> The fix suggested by Chris Wilson removes the kernel oops and was found to >> work well after 10mn of monkey-testing with the second monitor power and >> input buttons >> >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98990 >> Fixes: dfda0df34264 ("drm/mst: rework payload table allocation to conform better.") >> Cc: Dave Airlie <airlied@xxxxxxxxxx> >> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> >> Cc: Nathan D Ciobanu <nathan.d.ciobanu@xxxxxxxxxxxxxxx> >> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx> >> Cc: Sean Paul <seanpaul@xxxxxxxxxxxx> >> Cc: <stable@xxxxxxxxxxxxxxx> # v3.18+ >> Tested-by: Nathan D Ciobanu <nathan.d.ciobanu@xxxxxxxxxxxxxxx> >> Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx> >> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx> >> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx> > > You haz drm-misc commit rights, pls use them :-) Sure, I just wanted to have a fresh CI run on this. > Since it doesn't have deps, probably simplest to smash into drm-misc-fixes > and then send a pull req to Dave right away. If you want, you can roll > -fixes forward to -rc8 while at it. Will do. BR, Jani. > -Daniel > >> --- >> drivers/gpu/drm/drm_dp_mst_topology.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c >> index 122a1b04bebc..f2cc375907d0 100644 >> --- a/drivers/gpu/drm/drm_dp_mst_topology.c >> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c >> @@ -1817,7 +1817,7 @@ int drm_dp_update_payload_part1(struct drm_dp_mst_topology_mgr *mgr) >> mgr->payloads[i].vcpi = req_payload.vcpi; >> } else if (mgr->payloads[i].num_slots) { >> mgr->payloads[i].num_slots = 0; >> - drm_dp_destroy_payload_step1(mgr, port, port->vcpi.vcpi, &mgr->payloads[i]); >> + drm_dp_destroy_payload_step1(mgr, port, mgr->payloads[i].vcpi, &mgr->payloads[i]); >> req_payload.payload_state = mgr->payloads[i].payload_state; >> mgr->payloads[i].start_slot = 0; >> } >> -- >> 2.1.4 >> >> _______________________________________________ >> Intel-gfx mailing list >> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx >> https://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Jani Nikula, Intel Open Source Technology Center