On Fri, 17 Sep 2021, Matthew Brost wrote: > On Sat, Sep 18, 2021 at 01:52:48AM +0300, Jani Nikula wrote: > > 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. > > > > Sure. Will do. Long term we should just look to rip out crap this (i.e. > stealing bits from aligned addresses for flags). It just crossed my mind, that I never did due diligence on _other_ callers of i915_sw_fence_init(). In fact they're okay, but that's because their fence functions are all declared with the #define __i915_sw_fence_call __aligned(4) from i915_sw_fence.h, which I had not seen when I sent the patch. I'm not going to resend, but if I were you, I'd quietly edit that patch to use __i915_sw_fence_call in place of my __aligned(4). Thanks, Hugh > > Matt > > > 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
