[PATCH] drm/i915/ttm: Fix TTM_PL_FLAG_DESIRED

[Christian König]

Am 27.02.24 um 21:26 schrieb Ville Syrjala:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> inlined from ‘i915_ttm_get_pages’ at ../drivers/gpu/drm/i915/gem/i915_gem_ttm.c:847:2:
> ../drivers/gpu/drm/i915/gem/i915_gem_ttm.c:165:18: warning: ‘places[0].flags’ is used uninitialized [-Wuninitialized]
>    165 |         places[0].flags |= TTM_PL_FLAG_DESIRED;
>        |         ~~~~~~~~~^~~~~~
> ../drivers/gpu/drm/i915/gem/i915_gem_ttm.c: In function ‘i915_ttm_get_pages’:
> ../drivers/gpu/drm/i915/gem/i915_gem_ttm.c:837:26: note: ‘places’ declared here
>    837 |         struct ttm_place places[I915_TTM_MAX_PLACEMENTS + 1];
>        |                          ^~~~~~
>
> Furhermore we then proceed to call i915_ttm_place_from_region() which
> memset()s the whole thing back to zero anyway. So in the end we lose
> the TTM_PL_FLAG_DESIRED flag (and fortunately also whatever else stack
> garbage happened to be in the flags at this point).
>
> No idea what functional changes this will result in...

I've already send out the same patch yesterday. Please review that one.

Sorry for the noise, didn't realized that i915_ttm_place_from_region() 
was initializing the flags and not the caller while converting this.

Thanks,
Christian.

>
> Cc: Somalapuram Amaranath <Amaranath.Somalapuram at amd.com>
> Cc: Christian König <christian.koenig at amd.com>
> Cc: Zack Rusin <zack.rusin at broadcom.com>
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> Fixes: a78a8da51b36 ("drm/ttm: replace busy placement with flags v6")
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_ttm.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> index 27dcfd8a34bb..e6f177183c0f 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> @@ -162,10 +162,10 @@ i915_ttm_placement_from_obj(const struct drm_i915_gem_object *obj,
>   	unsigned int flags = obj->flags;
>   	unsigned int i;
>   
> -	places[0].flags |= TTM_PL_FLAG_DESIRED;
>   	i915_ttm_place_from_region(num_allowed ? obj->mm.placements[0] :
>   				   obj->mm.region, &places[0], obj->bo_offset,
>   				   obj->base.size, flags);
> +	places[0].flags |= TTM_PL_FLAG_DESIRED;
>   
>   	/* Cache this on object? */
>   	for (i = 0; i < num_allowed; ++i) {