[Intel-gfx] [bug report] drm/i915/ttm: add tt shmem backend

[Dan Carpenter]

Hello Matthew Auld,

The patch 7ae034590cea: "drm/i915/ttm: add tt shmem backend" from Oct
18, 2021, leads to the following Smatch static checker warning:

	drivers/gpu/drm/i915/gem/i915_gem_ttm.c:335 i915_ttm_eviction_valuable()
	warn: signedness bug returning '(-16)'

drivers/gpu/drm/i915/gem/i915_gem_ttm.c
    324 static bool i915_ttm_eviction_valuable(struct ttm_buffer_object *bo,
               ^^^^

    325                                        const struct ttm_place *place)
    326 {
    327         struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
    328 
    329         /*
    330          * EXTERNAL objects should never be swapped out by TTM, instead we need
    331          * to handle that ourselves. TTM will already skip such objects for us,
    332          * but we would like to avoid grabbing locks for no good reason.
    333          */
    334         if (bo->ttm && bo->ttm->page_flags & TTM_TT_FLAG_EXTERNAL)
--> 335                 return -EBUSY;
                        ^^^^^^^^^^^^^^
This should be return false probably.

    336 
    337         /* Will do for now. Our pinned objects are still on TTM's LRU lists */
    338         return i915_gem_object_evictable(obj);
    339 }

regards,
dan carpenter