Re: drm/i915: Initialize all contexts

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Ben Widawsky,

This is a semi-automatic email about new static checker warnings.

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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