Re: [drm-intel:for-linux-next 479/497] drivers/gpu/drm/i915/i915_gem_gtt.c:1086:26: sparse: Using plain integer as NULL pointer

[Michel Thierry <michel.thierry@intel.com>]

On 8/6/2015 11:00 PM, Daniel Vetter wrote:
> On Thu, Aug 6, 2015 at 10:17 PM, kbuild test robot
> <fengguang.wu@intel.com> wrote:
>>    1070          if (IS_ENABLED(CONFIG_X86_32))
>>    1071                  /* While we have a proliferation of size_t variables
>>    1072                   * we cannot represent the full ppgtt size on 32bit,
>>    1073                   * so limit it to the same size as the GGTT (currently
>>    1074                   * 2GiB).
>>    1075                   */
>>    1076                  ppgtt->base.total = to_i915(ppgtt->base.dev)->gtt.base.total;
>>    1077          ppgtt->base.cleanup = gen8_ppgtt_cleanup;
>>    1078          ppgtt->base.allocate_va_range = gen8_alloc_va_range;
>>    1079          ppgtt->base.insert_entries = gen8_ppgtt_insert_entries;
>>    1080          ppgtt->base.clear_range = gen8_ppgtt_clear_range;
>>    1081          ppgtt->base.unbind_vma = ppgtt_unbind_vma;
>>    1082          ppgtt->base.bind_vma = ppgtt_bind_vma;
>>    1083
>>    1084          ppgtt->switch_mm = gen8_mm_switch;
>>    1085
>>> 1086          ret = __pdp_init(false, &ppgtt->pdp);
>
> So the first argument of pdp_init ist struct drm_device *dev and yes
> the first thing it does is deref it.
>

*dev is used only for I915_PDPES_PER_PDP/USES_FULL_48BIT_PPGTT, which in 
this path is always false. I didn't expect kbuild to complain. I'll 
change it with the other modifications I'm about to send.

> How exactly was this tested again?
>
> Oh and the hunk right below with the CONFIG_X86_32 needs to got too -
> if we're 48b safe then we should be 32b safe too ;-)

Yes, after the offset change it'll be completely safe. I left it in this 
patch as that was only moving code around.
I'll include a proper "revert-me" patch, saying why it is safe now.

-Michel
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