[PATCH] drm/msm: Fix objtool warning in submit_lock_objects()

[Rob Clark]

On Tue, Aug 5, 2025 at 3:56 PM Sasha Levin <sashal at kernel.org> wrote:
>
> Restructure submit_lock_objects() to use a single loop with break
> statements to fix objtool warning:
>
>   drivers/gpu/drm/msm/msm.o: warning: objtool: submit_lock_objects+0x451:
>   sibling call from callable instruction with modified stack frame
>
> The drm_exec_until_all_locked() macro uses computed gotos internally
> for its retry loop. Having return statements inside this macro, or
> immediately after it in certain code paths, confuses objtool's static
> analysis of stack frames, causing it to incorrectly flag tail call
> optimizations.

Maybe we should instead just split out a separate
submit_lock_objects_vmbind() and restore the error path 'goto error'
instead of returning from within the loop?  Ie. basically revert
submit_lock_objects to the way it was before commit 92395af63a99
("drm/msm: Add VM_BIND submitqueue"), and then move the rest into a
new fxn (with 'goto error' instead of 'return ret'?  In retrospect the
vmbind case is kinda just shoehorned into the existing fxn.

I can type up this version if you have better things to do.

BR,
-R

> Fixes: 92395af63a99 ("drm/msm: Add VM_BIND submitqueue")
> Signed-off-by: Sasha Levin <sashal at kernel.org>
> ---
>  drivers/gpu/drm/msm/msm_gem_submit.c | 43 ++++++++++++----------------
>  1 file changed, 19 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
> index 5f8e939a5906..253347b6e328 100644
> --- a/drivers/gpu/drm/msm/msm_gem_submit.c
> +++ b/drivers/gpu/drm/msm/msm_gem_submit.c
> @@ -276,46 +276,41 @@ static int submit_lock_objects(struct msm_gem_submit *submit)
>  {
>         unsigned flags = DRM_EXEC_INTERRUPTIBLE_WAIT;
>         struct drm_exec *exec = &submit->exec;
> -       int ret;
> +       int ret = 0;
>
> -       if (msm_context_is_vmbind(submit->queue->ctx)) {
> +       if (msm_context_is_vmbind(submit->queue->ctx))
>                 flags |= DRM_EXEC_IGNORE_DUPLICATES;
>
> -               drm_exec_init(&submit->exec, flags, submit->nr_bos);
> +       drm_exec_init(&submit->exec, flags, submit->nr_bos);
>
> -               drm_exec_until_all_locked (&submit->exec) {
> +       drm_exec_until_all_locked (&submit->exec) {
> +               if (msm_context_is_vmbind(submit->queue->ctx)) {
>                         ret = drm_gpuvm_prepare_vm(submit->vm, exec, 1);
>                         drm_exec_retry_on_contention(exec);
>                         if (ret)
> -                               return ret;
> +                               break;
>
>                         ret = drm_gpuvm_prepare_objects(submit->vm, exec, 1);
>                         drm_exec_retry_on_contention(exec);
>                         if (ret)
> -                               return ret;
> -               }
> -
> -               return 0;
> -       }
> -
> -       drm_exec_init(&submit->exec, flags, submit->nr_bos);
> -
> -       drm_exec_until_all_locked (&submit->exec) {
> -               ret = drm_exec_lock_obj(&submit->exec,
> -                                       drm_gpuvm_resv_obj(submit->vm));
> -               drm_exec_retry_on_contention(&submit->exec);
> -               if (ret)
> -                       return ret;
> -               for (unsigned i = 0; i < submit->nr_bos; i++) {
> -                       struct drm_gem_object *obj = submit->bos[i].obj;
> -                       ret = drm_exec_prepare_obj(&submit->exec, obj, 1);
> +                               break;
> +               } else {
> +                       ret = drm_exec_lock_obj(&submit->exec,
> +                                               drm_gpuvm_resv_obj(submit->vm));
>                         drm_exec_retry_on_contention(&submit->exec);
>                         if (ret)
> -                               return ret;
> +                               break;
> +                       for (unsigned i = 0; i < submit->nr_bos; i++) {
> +                               struct drm_gem_object *obj = submit->bos[i].obj;
> +                               ret = drm_exec_prepare_obj(&submit->exec, obj, 1);
> +                               drm_exec_retry_on_contention(&submit->exec);
> +                               if (ret)
> +                                       break;
> +                       }
>                 }
>         }
>
> -       return 0;
> +       return ret;
>  }
>
>  static int submit_fence_sync(struct msm_gem_submit *submit)
> --
> 2.39.5
>