[drm-intel:for-linux-next 18/27] drivers/gpu/drm/i915/i915_gem_gtt.c:1087: warning: 'iter' is used uninitialized in this function

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tree:   git://anongit.freedesktop.org/drm-intel for-linux-next
head:   a883241c3922000b21b58b5740c55badfe09940f
commit: 0a03852e049af91da9ae70326c44bb5d9b0d377a [18/27] drm/i915: support 2M pages for the 48b PPGTT
config: x86_64-randconfig-a0-10072329 (attached as .config)
compiler: gcc-4.4 (Debian 4.4.7-8) 4.4.7
reproduce:
        git checkout 0a03852e049af91da9ae70326c44bb5d9b0d377a
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   drivers/gpu/drm/i915/i915_gem_gtt.c: In function 'gen8_ppgtt_insert_3lvl':
   drivers/gpu/drm/i915/i915_gem_gtt.c:1007: warning: 'iter.sg' is used uninitialized in this function
   drivers/gpu/drm/i915/i915_gem_gtt.c:1008: warning: 'iter.dma' is used uninitialized in this function
   drivers/gpu/drm/i915/i915_gem_gtt.c: In function 'gen8_ppgtt_insert_4lvl':
>> drivers/gpu/drm/i915/i915_gem_gtt.c:1087: warning: 'iter' is used uninitialized in this function
   drivers/gpu/drm/i915/i915_gem_gtt.c: In function 'intel_ppat_get':
   drivers/gpu/drm/i915/i915_gem_gtt.c:2969: warning: 'entry' may be used uninitialized in this function

vim +/iter +1087 drivers/gpu/drm/i915/i915_gem_gtt.c

9df15b499 Ben Widawsky   2013-11-02   998  
894ccebee Chris Wilson   2017-02-15   999  static void gen8_ppgtt_insert_3lvl(struct i915_address_space *vm,
4a234c5fa Matthew Auld   2017-06-22  1000  				   struct i915_vma *vma,
f9b5b782c Michel Thierry 2015-07-30  1001  				   enum i915_cache_level cache_level,
f9b5b782c Michel Thierry 2015-07-30  1002  				   u32 unused)
f9b5b782c Michel Thierry 2015-07-30  1003  {
17369ba08 Chuanxiao Dong 2017-07-07  1004  	struct i915_hw_ppgtt *ppgtt = i915_vm_to_ppgtt(vm);
894ccebee Chris Wilson   2017-02-15  1005  	struct sgt_dma iter = {
4a234c5fa Matthew Auld   2017-06-22  1006  		.sg = vma->pages->sgl,
894ccebee Chris Wilson   2017-02-15 @1007  		.dma = sg_dma_address(iter.sg),
894ccebee Chris Wilson   2017-02-15  1008  		.max = iter.dma + iter.sg->length,
894ccebee Chris Wilson   2017-02-15  1009  	};
4a234c5fa Matthew Auld   2017-06-22  1010  	struct gen8_insert_pte idx = gen8_insert_pte(vma->node.start);
de5ba8eb9 Michel Thierry 2015-08-03  1011  
9e89f9ee3 Chris Wilson   2017-02-25  1012  	gen8_ppgtt_insert_pte_entries(ppgtt, &ppgtt->pdp, &iter, &idx,
9e89f9ee3 Chris Wilson   2017-02-25  1013  				      cache_level);
de5ba8eb9 Michel Thierry 2015-08-03  1014  }
894ccebee Chris Wilson   2017-02-15  1015  
0a03852e0 Matthew Auld   2017-10-06  1016  static void gen8_ppgtt_insert_huge_entries(struct i915_vma *vma,
0a03852e0 Matthew Auld   2017-10-06  1017  					   struct i915_page_directory_pointer **pdps,
0a03852e0 Matthew Auld   2017-10-06  1018  					   struct sgt_dma *iter,
0a03852e0 Matthew Auld   2017-10-06  1019  					   enum i915_cache_level cache_level)
0a03852e0 Matthew Auld   2017-10-06  1020  {
0a03852e0 Matthew Auld   2017-10-06  1021  	const gen8_pte_t pte_encode = gen8_pte_encode(0, cache_level);
0a03852e0 Matthew Auld   2017-10-06  1022  	u64 start = vma->node.start;
0a03852e0 Matthew Auld   2017-10-06  1023  	dma_addr_t rem = iter->sg->length;
0a03852e0 Matthew Auld   2017-10-06  1024  
0a03852e0 Matthew Auld   2017-10-06  1025  	do {
0a03852e0 Matthew Auld   2017-10-06  1026  		struct gen8_insert_pte idx = gen8_insert_pte(start);
0a03852e0 Matthew Auld   2017-10-06  1027  		struct i915_page_directory_pointer *pdp = pdps[idx.pml4e];
0a03852e0 Matthew Auld   2017-10-06  1028  		struct i915_page_directory *pd = pdp->page_directory[idx.pdpe];
0a03852e0 Matthew Auld   2017-10-06  1029  		unsigned int page_size;
0a03852e0 Matthew Auld   2017-10-06  1030  		gen8_pte_t encode = pte_encode;
0a03852e0 Matthew Auld   2017-10-06  1031  		gen8_pte_t *vaddr;
0a03852e0 Matthew Auld   2017-10-06  1032  		u16 index, max;
0a03852e0 Matthew Auld   2017-10-06  1033  
0a03852e0 Matthew Auld   2017-10-06  1034  		if (vma->page_sizes.sg & I915_GTT_PAGE_SIZE_2M &&
0a03852e0 Matthew Auld   2017-10-06  1035  		    IS_ALIGNED(iter->dma, I915_GTT_PAGE_SIZE_2M) &&
0a03852e0 Matthew Auld   2017-10-06  1036  		    rem >= I915_GTT_PAGE_SIZE_2M && !idx.pte) {
0a03852e0 Matthew Auld   2017-10-06  1037  			index = idx.pde;
0a03852e0 Matthew Auld   2017-10-06  1038  			max = I915_PDES;
0a03852e0 Matthew Auld   2017-10-06  1039  			page_size = I915_GTT_PAGE_SIZE_2M;
0a03852e0 Matthew Auld   2017-10-06  1040  
0a03852e0 Matthew Auld   2017-10-06  1041  			encode |= GEN8_PDE_PS_2M;
0a03852e0 Matthew Auld   2017-10-06  1042  
0a03852e0 Matthew Auld   2017-10-06  1043  			vaddr = kmap_atomic_px(pd);
0a03852e0 Matthew Auld   2017-10-06  1044  		} else {
0a03852e0 Matthew Auld   2017-10-06  1045  			struct i915_page_table *pt = pd->page_table[idx.pde];
0a03852e0 Matthew Auld   2017-10-06  1046  
0a03852e0 Matthew Auld   2017-10-06  1047  			index = idx.pte;
0a03852e0 Matthew Auld   2017-10-06  1048  			max = GEN8_PTES;
0a03852e0 Matthew Auld   2017-10-06  1049  			page_size = I915_GTT_PAGE_SIZE;
0a03852e0 Matthew Auld   2017-10-06  1050  
0a03852e0 Matthew Auld   2017-10-06  1051  			vaddr = kmap_atomic_px(pt);
0a03852e0 Matthew Auld   2017-10-06  1052  		}
0a03852e0 Matthew Auld   2017-10-06  1053  
0a03852e0 Matthew Auld   2017-10-06  1054  		do {
0a03852e0 Matthew Auld   2017-10-06  1055  			GEM_BUG_ON(iter->sg->length < page_size);
0a03852e0 Matthew Auld   2017-10-06  1056  			vaddr[index++] = encode | iter->dma;
0a03852e0 Matthew Auld   2017-10-06  1057  
0a03852e0 Matthew Auld   2017-10-06  1058  			start += page_size;
0a03852e0 Matthew Auld   2017-10-06  1059  			iter->dma += page_size;
0a03852e0 Matthew Auld   2017-10-06  1060  			rem -= page_size;
0a03852e0 Matthew Auld   2017-10-06  1061  			if (iter->dma >= iter->max) {
0a03852e0 Matthew Auld   2017-10-06  1062  				iter->sg = __sg_next(iter->sg);
0a03852e0 Matthew Auld   2017-10-06  1063  				if (!iter->sg)
0a03852e0 Matthew Auld   2017-10-06  1064  					break;
0a03852e0 Matthew Auld   2017-10-06  1065  
0a03852e0 Matthew Auld   2017-10-06  1066  				rem = iter->sg->length;
0a03852e0 Matthew Auld   2017-10-06  1067  				iter->dma = sg_dma_address(iter->sg);
0a03852e0 Matthew Auld   2017-10-06  1068  				iter->max = iter->dma + rem;
0a03852e0 Matthew Auld   2017-10-06  1069  
0a03852e0 Matthew Auld   2017-10-06  1070  				if (unlikely(!IS_ALIGNED(iter->dma, page_size)))
0a03852e0 Matthew Auld   2017-10-06  1071  					break;
0a03852e0 Matthew Auld   2017-10-06  1072  			}
0a03852e0 Matthew Auld   2017-10-06  1073  		} while (rem >= page_size && index < max);
0a03852e0 Matthew Auld   2017-10-06  1074  
0a03852e0 Matthew Auld   2017-10-06  1075  		kunmap_atomic(vaddr);
0a03852e0 Matthew Auld   2017-10-06  1076  	} while (iter->sg);
0a03852e0 Matthew Auld   2017-10-06  1077  }
0a03852e0 Matthew Auld   2017-10-06  1078  
894ccebee Chris Wilson   2017-02-15  1079  static void gen8_ppgtt_insert_4lvl(struct i915_address_space *vm,
4a234c5fa Matthew Auld   2017-06-22  1080  				   struct i915_vma *vma,
894ccebee Chris Wilson   2017-02-15  1081  				   enum i915_cache_level cache_level,
894ccebee Chris Wilson   2017-02-15  1082  				   u32 unused)
894ccebee Chris Wilson   2017-02-15  1083  {
894ccebee Chris Wilson   2017-02-15  1084  	struct i915_hw_ppgtt *ppgtt = i915_vm_to_ppgtt(vm);
894ccebee Chris Wilson   2017-02-15  1085  	struct sgt_dma iter = {
4a234c5fa Matthew Auld   2017-06-22  1086  		.sg = vma->pages->sgl,
894ccebee Chris Wilson   2017-02-15 @1087  		.dma = sg_dma_address(iter.sg),
894ccebee Chris Wilson   2017-02-15  1088  		.max = iter.dma + iter.sg->length,
894ccebee Chris Wilson   2017-02-15  1089  	};
894ccebee Chris Wilson   2017-02-15  1090  	struct i915_page_directory_pointer **pdps = ppgtt->pml4.pdps;
0a03852e0 Matthew Auld   2017-10-06  1091  
0a03852e0 Matthew Auld   2017-10-06  1092  	if (vma->page_sizes.sg > I915_GTT_PAGE_SIZE) {
0a03852e0 Matthew Auld   2017-10-06  1093  		gen8_ppgtt_insert_huge_entries(vma, pdps, &iter, cache_level);
0a03852e0 Matthew Auld   2017-10-06  1094  	} else {
4a234c5fa Matthew Auld   2017-06-22  1095  		struct gen8_insert_pte idx = gen8_insert_pte(vma->node.start);
894ccebee Chris Wilson   2017-02-15  1096  
0a03852e0 Matthew Auld   2017-10-06  1097  		while (gen8_ppgtt_insert_pte_entries(ppgtt, pdps[idx.pml4e++],
0a03852e0 Matthew Auld   2017-10-06  1098  						     &iter, &idx, cache_level))
9e89f9ee3 Chris Wilson   2017-02-25  1099  			GEM_BUG_ON(idx.pml4e >= GEN8_PML4ES_PER_PML4);
f9b5b782c Michel Thierry 2015-07-30  1100  	}
0a03852e0 Matthew Auld   2017-10-06  1101  }
f9b5b782c Michel Thierry 2015-07-30  1102  

:::::: The code at line 1087 was first introduced by commit
:::::: 894ccebee2b0e606ba9638d20dd87b33568482d7 drm/i915: Micro-optimise gen8_ppgtt_insert_entries()

:::::: TO: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
:::::: CC: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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