On Mon, Aug 10, 2020 at 09:53:44PM +0100, Chris Wilson wrote:
> Quoting Matt Roper (2020-08-10 19:08:51)
> > Userspace may still create GEM dumb buffers even on platforms with
> > disabled or non-existent display. When creating dumb buffers we try to
> > check the max fb stride for the platform by looking at the first pipe on
> > the platform. We previously fixed a crash related to accessing the
> > non-existent PIPE_A in commit 8ac495f624a4 ("drm/i915: Don't oops in
> > dumb_create ioctl if we have no crtcs") but the crash is back as of
> > commit eae3da27ba84 ("drm/i915: Get first crtc instead of PIPE_A crtc")
> > because we now try to iterate over the [uninitialized] crtc list.
>
> drm_mode_config_init() is still being called
> i915_driver_probe
> -> i915_driver_modeset_probe_noirq
> -> intel_modeset_init_noirq
> -> intel_mode_config_init
> -> drm_mode_config_init
> regardless of the status for HAS_DISPLAY or INTEL_DISPLAY_ENABLED. So
> drm_crtc_index(0) should be returning NULL?
Ah, you're right. The kernel that I was looking at the backtrace from
was a bit different than drm-tip and had a different initialization
flow. Looks like drm-tip doesn't suffer from the same problem and we
don't need this patch after all.
Matt
> -Chris
--
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation
(916) 356-2795
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