drm/i915: Advance start address on crossing PML (48b ppgtt) boundary

When advancing onto the next 4th level page table entry, we need to
reset our indices to 0. Currently we restart from the original address
which means we start with an offset into the next PML table.

Fixes: 894cceb ("drm/i915: Micro-optimise gen8_ppgtt_insert_entries()")
Reported-by: Matthew Auld <matthew.william.auld@gmail.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99948
Testcase: igt/drv_selftest/live_gtt
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Tested-by: Matthew Auld <matthew.william.auld@gmail.com>
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170225181122.4788-4-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem_gtt.c

@@ -815,26 +815,41 @@ struct sgt_dma {
 	dma_addr_t dma, max;
 };
 
+struct gen8_insert_pte {
+	u16 pml4e;
+	u16 pdpe;
+	u16 pde;
+	u16 pte;
+};
+
+static __always_inline struct gen8_insert_pte gen8_insert_pte(u64 start)
+{
+	return (struct gen8_insert_pte) {
+		 gen8_pml4e_index(start),
+		 gen8_pdpe_index(start),
+		 gen8_pde_index(start),
+		 gen8_pte_index(start),
+	};
+}
+
 static __always_inline bool
 gen8_ppgtt_insert_pte_entries(struct i915_hw_ppgtt *ppgtt,
 			      struct i915_page_directory_pointer *pdp,
 			      struct sgt_dma *iter,
-			      u64 start,
+			      struct gen8_insert_pte *idx,
 			      enum i915_cache_level cache_level)
 {
-	unsigned int pdpe = gen8_pdpe_index(start);
-	unsigned int pde = gen8_pde_index(start);
-	unsigned int pte = gen8_pte_index(start);
 	struct i915_page_directory *pd;
 	const gen8_pte_t pte_encode = gen8_pte_encode(0, cache_level);
 	gen8_pte_t *vaddr;
 	bool ret;
 
-	GEM_BUG_ON(pdpe >= I915_PDPES_PER_PDP(vm));
-	pd = pdp->page_directory[pdpe];
-	vaddr = kmap_atomic_px(pd->page_table[pde]);
+	GEM_BUG_ON(idx->pdpe >= I915_PDPES_PER_PDP(vm));
+	pd = pdp->page_directory[idx->pdpe];
+	vaddr = kmap_atomic_px(pd->page_table[idx->pde]);
 	do {
-		vaddr[pte] = pte_encode | iter->dma;
+		vaddr[idx->pte] = pte_encode | iter->dma;
+
 		iter->dma += PAGE_SIZE;
 		if (iter->dma >= iter->max) {
 			iter->sg = __sg_next(iter->sg);
@@ -847,22 +862,25 @@ gen8_ppgtt_insert_pte_entries(struct i915_hw_ppgtt *ppgtt,
 			iter->max = iter->dma + iter->sg->length;
 		}
 
-		if (++pte == GEN8_PTES) {
-			if (++pde == I915_PDES) {
+		if (++idx->pte == GEN8_PTES) {
+			idx->pte = 0;
+
+			if (++idx->pde == I915_PDES) {
+				idx->pde = 0;
+
 				/* Limited by sg length for 3lvl */
-				if (++pdpe == GEN8_PML4ES_PER_PML4) {
+				if (++idx->pdpe == GEN8_PML4ES_PER_PML4) {
+					idx->pdpe = 0;
 					ret = true;
 					break;
 				}
 
-				GEM_BUG_ON(pdpe >= I915_PDPES_PER_PDP(vm));
-				pd = pdp->page_directory[pdpe];
-				pde = 0;
+				GEM_BUG_ON(idx->pdpe >= I915_PDPES_PER_PDP(vm));
+				pd = pdp->page_directory[idx->pdpe];
 			}
 
 			kunmap_atomic(vaddr);
-			vaddr = kmap_atomic_px(pd->page_table[pde]);
-			pte = 0;
+			vaddr = kmap_atomic_px(pd->page_table[idx->pde]);
 		}
 	} while (1);
 	kunmap_atomic(vaddr);
@@ -882,9 +900,10 @@ static void gen8_ppgtt_insert_3lvl(struct i915_address_space *vm,
 		.dma = sg_dma_address(iter.sg),
 		.max = iter.dma + iter.sg->length,
 	};
+	struct gen8_insert_pte idx = gen8_insert_pte(start);
 
-	gen8_ppgtt_insert_pte_entries(ppgtt, &ppgtt->pdp, &iter,
-				      start, cache_level);
+	gen8_ppgtt_insert_pte_entries(ppgtt, &ppgtt->pdp, &iter, &idx,
+				      cache_level);
 }
 
 static void gen8_ppgtt_insert_4lvl(struct i915_address_space *vm,
@@ -900,11 +919,11 @@ static void gen8_ppgtt_insert_4lvl(struct i915_address_space *vm,
 		.max = iter.dma + iter.sg->length,
 	};
 	struct i915_page_directory_pointer **pdps = ppgtt->pml4.pdps;
-	unsigned int pml4e = gen8_pml4e_index(start);
+	struct gen8_insert_pte idx = gen8_insert_pte(start);
 
-	while (gen8_ppgtt_insert_pte_entries(ppgtt, pdps[pml4e++], &iter,
-					     start, cache_level))
-		GEM_BUG_ON(pml4e >= GEN8_PML4ES_PER_PML4);
+	while (gen8_ppgtt_insert_pte_entries(ppgtt, pdps[idx.pml4e++], &iter,
+					     &idx, cache_level))
+		GEM_BUG_ON(idx.pml4e >= GEN8_PML4ES_PER_PML4);
 }
 
 static void gen8_free_page_tables(struct i915_address_space *vm,