Re: [PATCH] drm/i915/dpt: Make DPT object unshrinkable

[Tvrtko Ursulin <tursulin@ursulin.net>]

On 22/05/2024 16:29, Vidya Srinivas wrote:
> In some scenarios, the DPT object gets shrunk but
> the actual framebuffer did not and thus its still
> there on the DPT's vm->bound_list. Then it tries to
> rewrite the PTEs via a stale CPU mapping. This causes panic.
> 
> Suggested-by: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: stable@vger.kernel.org
> Fixes: 0dc987b699ce ("drm/i915/display: Add smem fallback allocation for dpt")
> Signed-off-by: Vidya Srinivas <vidya.srinivas@intel.com>
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_object.h | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> index 3560a062d287..e6b485fc54d4 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> @@ -284,7 +284,8 @@ bool i915_gem_object_has_iomem(const struct drm_i915_gem_object *obj);
>   static inline bool
>   i915_gem_object_is_shrinkable(const struct drm_i915_gem_object *obj)
>   {
> -	return i915_gem_object_type_has(obj, I915_GEM_OBJECT_IS_SHRINKABLE);
> +	return i915_gem_object_type_has(obj, I915_GEM_OBJECT_IS_SHRINKABLE) &&
> +		!obj->is_dpt;

Is there a reason i915_gem_object_make_unshrinkable() cannot be used to 
mark the object at a suitable place?

Regards,

Tvrtko

>   }
>   
>   static inline bool