Re: drm/i915: Initialize all contexts

Daniel Vetter
2015-03-24T09:10:33Z

On Mon, Mar 23, 2015 at 06:54:52PM +0300, Dan Carpenter wrote:
> Hello Ben Widawsky,
>
> This is a semi-automatic email about new static checker warnings.

Adding Michel and Mika.
-Daniel

>
> The patch 6702cf16e0ba: "drm/i915: Initialize all contexts" from Mar
> 16, 2015, leads to the following Smatch complaint:
>
> drivers/gpu/drm/i915/i915_gem_context.c:730 do_switch()
> error: we previously assumed 'to->ppgtt' could be null (see line 713)
>
> drivers/gpu/drm/i915/i915_gem_context.c
> 712 * occur when this occurs. */
> 713 } else if (to->ppgtt &&
> ^^^^^^^^^
> Patch introduces a new NULL check.
>
> 714 test_and_clear_bit(ring->id, &to->ppgtt->pd_dirty_rings))
> 715 hw_flags |= MI_FORCE_RESTORE;
> 716
> 717 /* We should never emit switch_mm more than once */
> 718 WARN_ON(needs_pd_load_pre(ring, to) &&
> 719 needs_pd_load_post(ring, to, hw_flags));
> 720
> 721 ret = mi_set_context(ring, to, hw_flags);
> 722 if (ret)
> 723 goto unpin_out;
> 724
> 725 /* GEN8 does *not* require an explicit reload if the PDPs have been
> 726 * setup, and we do not wish to move them.
> 727 */
> 728 if (needs_pd_load_post(ring, to, hw_flags)) {
> 729 trace_switch_mm(ring, to);
> 730 ret = to->ppgtt->switch_mm(to->ppgtt, ring);
> ^^^^^^^^^^^
> Existing unchecked dereference.
>
> 731 /* The hardware context switch is emitted, but we haven't
> 732 * actually changed the state - so it's probably safe to bail
>
> regards,
> dan carpenter
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--
Daniel Vetter
Software Engineer, Intel Corporation