[PATCH v5 17/20] drm/gpusvm: Introduce drm_gpusvm_range_find_or_insert_start() function

[Himal Prasad Ghimiray]

The drm_gpusvm_range_find_or_insert_start() function is used to
determine the starting address of a CPU VMA within a specified user
range. If the range does not contain any VMA, the function returns
ULONG_MAX.

Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray at intel.com>
---
 drivers/gpu/drm/drm_gpusvm.c | 29 +++++++++++++++++++++++++++++
 include/drm/drm_gpusvm.h     |  5 +++++
 2 files changed, 34 insertions(+)

diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
index 40a56f38ff8e..bb7c589b8d15 100644
--- a/drivers/gpu/drm/drm_gpusvm.c
+++ b/drivers/gpu/drm/drm_gpusvm.c
@@ -980,6 +980,35 @@ static void drm_gpusvm_driver_lock_held(struct drm_gpusvm *gpusvm)
 }
 #endif
 
+/**
+ * drm_gpusvm_range_find_or_insert_start() - Find or insert start address for range
+ * @gpusvm: Pointer to the GPU SVM structure
+ * @start: The inclusive start user address.
+ * @end: The exclusive end user address.
+ *
+ * Returns: The start address of first VMA within the provided range,
+ * ULONG_MAX otherwise. Assumes start_addr < end_addr.
+ */
+unsigned long
+drm_gpusvm_range_find_or_insert_start(struct drm_gpusvm *gpusvm,
+				      unsigned long start,
+				      unsigned long end)
+{
+	struct mm_struct *mm = gpusvm->mm;
+	struct vm_area_struct *vma;
+	unsigned long addr = ULONG_MAX;
+
+	mmap_read_lock(mm);
+
+	vma = find_vma_intersection(mm, start, end);
+	if (vma)
+		addr =  vma->vm_start;
+
+	mmap_read_unlock(mm);
+	return addr;
+}
+EXPORT_SYMBOL_GPL(drm_gpusvm_range_find_or_insert_start);
+
 /**
  * drm_gpusvm_range_find_or_insert() - Find or insert GPU SVM range
  * @gpusvm: Pointer to the GPU SVM structure
diff --git a/include/drm/drm_gpusvm.h b/include/drm/drm_gpusvm.h
index cce217bc136f..b0e9ee5c6226 100644
--- a/include/drm/drm_gpusvm.h
+++ b/include/drm/drm_gpusvm.h
@@ -315,6 +315,11 @@ void drm_gpusvm_fini(struct drm_gpusvm *gpusvm);
 
 void drm_gpusvm_free(struct drm_gpusvm *gpusvm);
 
+unsigned long
+drm_gpusvm_range_find_or_insert_start(struct drm_gpusvm *gpusvm,
+				      unsigned long start,
+				      unsigned long end);
+
 struct drm_gpusvm_range *
 drm_gpusvm_range_find_or_insert(struct drm_gpusvm *gpusvm,
 				unsigned long fault_addr,
-- 
2.34.1