[PATCH] drm/amdgpu: remove PT BOs when unmapping

[Huang, JinHuiEric]

The issue is PT BOs are not freed when unmapping VA,
which causes vram usage accumulated is huge in some
memory stress test, such as kfd big buffer stress test.
Function amdgpu_vm_bo_update_mapping() is called by both
amdgpu_vm_bo_update() and amdgpu_vm_clear_freed(). The
solution is replacing amdgpu_vm_bo_update_mapping() in
amdgpu_vm_clear_freed() with removing PT BOs function
to save vram usage.

Change-Id: Ic24e35bff8ca85265b418a642373f189d972a924
Signed-off-by: Eric Huang <JinhuiEric.Huang at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 56 +++++++++++++++++++++++++++++-----
 1 file changed, 48 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index 0f4c3b2..8a480c7 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -1930,6 +1930,51 @@ static void amdgpu_vm_prt_fini(struct amdgpu_device *adev, struct amdgpu_vm *vm)
 }
 
 /**
+ * amdgpu_vm_remove_ptes - free PT BOs
+ *
+ * @adev: amdgpu device structure
+ * @vm: amdgpu vm structure
+ * @start: start of mapped range
+ * @end: end of mapped entry
+ *
+ * Free the page table level.
+ */
+static int amdgpu_vm_remove_ptes(struct amdgpu_device *adev,
+		struct amdgpu_vm *vm, uint64_t start, uint64_t end)
+{
+	struct amdgpu_vm_pt_cursor cursor;
+	unsigned shift, num_entries;
+
+	amdgpu_vm_pt_start(adev, vm, start, &cursor);
+	while (cursor.level < AMDGPU_VM_PTB) {
+		if (!amdgpu_vm_pt_descendant(adev, &cursor))
+			return -ENOENT;
+	}
+
+	while (cursor.pfn < end) {
+		amdgpu_vm_free_table(cursor.entry);
+		num_entries = amdgpu_vm_num_entries(adev, cursor.level - 1);
+
+		if (cursor.entry != &cursor.parent->entries[num_entries - 1]) {
+			/* Next ptb entry */
+			shift = amdgpu_vm_level_shift(adev, cursor.level - 1);
+			cursor.pfn += 1ULL << shift;
+			cursor.pfn &= ~((1ULL << shift) - 1);
+			cursor.entry++;
+		} else {
+			/* Next ptb entry in next pd0 entry */
+			amdgpu_vm_pt_ancestor(&cursor);
+			shift = amdgpu_vm_level_shift(adev, cursor.level - 1);
+			cursor.pfn += 1ULL << shift;
+			cursor.pfn &= ~((1ULL << shift) - 1);
+			amdgpu_vm_pt_descendant(adev, &cursor);
+		}
+	}
+
+	return 0;
+}
+
+/**
  * amdgpu_vm_clear_freed - clear freed BOs in the PT
  *
  * @adev: amdgpu_device pointer
@@ -1949,7 +1994,6 @@ int amdgpu_vm_clear_freed(struct amdgpu_device *adev,
 			  struct dma_fence **fence)
 {
 	struct amdgpu_bo_va_mapping *mapping;
-	uint64_t init_pte_value = 0;
 	struct dma_fence *f = NULL;
 	int r;
 
@@ -1958,13 +2002,10 @@ int amdgpu_vm_clear_freed(struct amdgpu_device *adev,
 			struct amdgpu_bo_va_mapping, list);
 		list_del(&mapping->list);
 
-		if (vm->pte_support_ats &&
-		    mapping->start < AMDGPU_GMC_HOLE_START)
-			init_pte_value = AMDGPU_PTE_DEFAULT_ATC;
+		r = amdgpu_vm_remove_ptes(adev, vm,
+				(mapping->start + 0x1ff) & (~0x1ffll),
+				(mapping->last + 1) & (~0x1ffll));
 
-		r = amdgpu_vm_bo_update_mapping(adev, vm, false, NULL,
-						mapping->start, mapping->last,
-						init_pte_value, 0, NULL, &f);
 		amdgpu_vm_free_mapping(adev, vm, mapping, f);
 		if (r) {
 			dma_fence_put(f);
@@ -1980,7 +2021,6 @@ int amdgpu_vm_clear_freed(struct amdgpu_device *adev,
 	}
 
 	return 0;
-
 }
 
 /**
-- 
2.7.4