Revert "drm/amdkfd:remove unused code"

This reverts commit f9caf6cd.

Needed for the next revert patch.
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_svm.c

@@ -1147,6 +1147,66 @@ svm_range_add_child(struct svm_range *prange, struct mm_struct *mm,
 	list_add_tail(&pchild->child_list, &prange->child_list);
 }
 
+/**
+ * svm_range_split_by_granularity - collect ranges within granularity boundary
+ *
+ * @p: the process with svms list
+ * @mm: mm structure
+ * @addr: the vm fault address in pages, to split the prange
+ * @parent: parent range if prange is from child list
+ * @prange: prange to split
+ *
+ * Trims @prange to be a single aligned block of prange->granularity if
+ * possible. The head and tail are added to the child_list in @parent.
+ *
+ * Context: caller must hold mmap_read_lock and prange->lock
+ *
+ * Return:
+ * 0 - OK, otherwise error code
+ */
+int
+svm_range_split_by_granularity(struct kfd_process *p, struct mm_struct *mm,
+			       unsigned long addr, struct svm_range *parent,
+			       struct svm_range *prange)
+{
+	struct svm_range *head, *tail;
+	unsigned long start, last, size;
+	int r;
+
+	/* Align splited range start and size to granularity size, then a single
+	 * PTE will be used for whole range, this reduces the number of PTE
+	 * updated and the L1 TLB space used for translation.
+	 */
+	size = 1UL << prange->granularity;
+	start = ALIGN_DOWN(addr, size);
+	last = ALIGN(addr + 1, size) - 1;
+
+	pr_debug("svms 0x%p split [0x%lx 0x%lx] to [0x%lx 0x%lx] size 0x%lx\n",
+		 prange->svms, prange->start, prange->last, start, last, size);
+
+	if (start > prange->start) {
+		r = svm_range_split(prange, start, prange->last, &head);
+		if (r)
+			return r;
+		svm_range_add_child(parent, mm, head, SVM_OP_ADD_RANGE);
+	}
+
+	if (last < prange->last) {
+		r = svm_range_split(prange, prange->start, last, &tail);
+		if (r)
+			return r;
+		svm_range_add_child(parent, mm, tail, SVM_OP_ADD_RANGE);
+	}
+
+	/* xnack on, update mapping on GPUs with ACCESS_IN_PLACE */
+	if (p->xnack_enabled && prange->work_item.op == SVM_OP_ADD_RANGE) {
+		prange->work_item.op = SVM_OP_ADD_RANGE_AND_MAP;
+		pr_debug("change prange 0x%p [0x%lx 0x%lx] op %d\n",
+			 prange, prange->start, prange->last,
+			 SVM_OP_ADD_RANGE_AND_MAP);
+	}
+	return 0;
+}
 static bool
 svm_nodes_in_same_hive(struct kfd_node *node_a, struct kfd_node *node_b)
 {

drivers/gpu/drm/amd/amdkfd/kfd_svm.h

@@ -172,6 +172,9 @@ struct kfd_node *svm_range_get_node_by_id(struct svm_range *prange,
 int svm_range_vram_node_new(struct kfd_node *node, struct svm_range *prange,
 			    bool clear);
 void svm_range_vram_node_free(struct svm_range *prange);
+int svm_range_split_by_granularity(struct kfd_process *p, struct mm_struct *mm,
+			       unsigned long addr, struct svm_range *parent,
+			       struct svm_range *prange);
 int svm_range_restore_pages(struct amdgpu_device *adev, unsigned int pasid,
 			    uint32_t vmid, uint32_t node_id, uint64_t addr,
 			    bool write_fault);