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. 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) > {
