[Intel-gfx] [PATCH 05/25] drm/i915: Prevent machine hang from Broxton's vtd w/a and error capture

[Joonas Lahtinen]

Quoting Chris Wilson (2018-11-02 18:12:12)
> Since capturing the error state requires fiddling around with the GGTT
> to read arbitrary buffers and is itself run under stop_machine(), it
> deadlocks the machine (effectively a hard hang) when run in conjunction
> with Broxton's VTd workaround to serialize GGTT access.
> 
> v2: Store the ERR_PTR in first_error so that the error can be reported
> to the user via sysfs.
> 
> Fixes: 0ef34ad6222a ("drm/i915: Serialize GTT/Aperture accesses on BXT")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Jon Bloomfield <jon.bloomfield at intel.com>
> Cc: John Harrison <john.C.Harrison at intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>

Might be worthy splurting something to the dmesg?

Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

Regards, Joonas