On Fri, 17 Sep 2021, Matthew Brost <matthew.brost@xxxxxxxxx> wrote: > On Fri, Sep 17, 2021 at 02:26:48PM -0700, Hugh Dickins wrote: >> On Thu, 16 Sep 2021, Jani Nikula wrote: >> > On Thu, 16 Sep 2021, Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> wrote: >> > > On 16/09/2021 05:37, Hugh Dickins wrote: >> > >> Two Lenovo ThinkPads, old T420s (2011), newer X1 Carbon 5th gen (2017): >> > >> i915 working fine on both up to 5.14, but blank screens booting 5.15-rc1, >> > >> kernel crashed in some way. >> ... >> > > Kernel logs with drm.debug=0xe, with the broken black screen state, >> > > would probably answer a lot of questions if you could gather it from >> > > both machines? >> > >> > And for that, I think it's best to file separate bugs at [1] and attach >> > the logs there. It helps keep the info in one place. Thanks. >> > >> > BR, >> > Jani. >> > >> > [1] https://gitlab.freedesktop.org/drm/intel/issues/new >> >> Thanks for the quick replies: but of course, getting kernel logs was >> the difficult part, this being bootup, with just a blank screen, and >> no logging to disk at this stage. I've never needed it before, but >> netconsole to the rescue. >> >> Problem then obvious, both machines now working, >> please let me skip the bug reports, here's a patch: >> > > Thanks for finding / fixing this Hugh. I will post this patch in a way > our CI system can understand. Thanks indeed! Matt, please get rid of the BUG_ON while at it, and make it a WARN. Oopsing doesn't do anyone any good. BR, Jani. > > Matt > >> [PATCH] drm/i915: fix blank screen booting crashes >> >> 5.15-rc1 crashes with blank screen when booting up on two ThinkPads >> using i915. Bisections converge convincingly, but arrive at different >> and surprising "culprits", none of them the actual culprit. >> >> netconsole (with init_netconsole() hacked to call i915_init() when >> logging has started, instead of by module_init()) tells the story: >> >> kernel BUG at drivers/gpu/drm/i915/i915_sw_fence.c:245! >> with RSI: ffffffff814d408b pointing to sw_fence_dummy_notify(). >> I've been building with CONFIG_CC_OPTIMIZE_FOR_SIZE=y, and that >> function needs to be 4-byte aligned. >> >> Fixes: 62eaf0ae217d ("drm/i915/guc: Support request cancellation") >> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> >> --- >> >> drivers/gpu/drm/i915/gt/intel_context.c | 1 + >> 1 file changed, 1 insertion(+) >> >> --- a/drivers/gpu/drm/i915/gt/intel_context.c >> +++ b/drivers/gpu/drm/i915/gt/intel_context.c >> @@ -362,6 +362,7 @@ static int __intel_context_active(struct >> return 0; >> } >> >> +__aligned(4) /* Respect the I915_SW_FENCE_MASK */ >> static int sw_fence_dummy_notify(struct i915_sw_fence *sf, >> enum i915_sw_fence_notify state) >> { -- Jani Nikula, Intel Open Source Graphics Center
