drm/amdgpu: fix max_entries calculation v4

Calculate the correct value for max_entries or we might run after the
page_address array.

v2: Xinhui pointed out we don't need the shift
v3: use local copy of start and simplify some calculation
v4: fix the case that we map less VA range than BO size
Signed-off-by: NChristian König <christian.koenig@amd.com>
Fixes: 1e691e24 drm/amdgpu: stop allocating dummy GTT nodes
Reviewed-by: Nxinhui pan <xinhui.pan@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c

@@ -1693,13 +1693,13 @@ static int amdgpu_vm_bo_split_mapping(struct amdgpu_device *adev,
 		uint64_t max_entries;
 		uint64_t addr, last;
 
+		max_entries = mapping->last - start + 1;
 		if (nodes) {
 			addr = nodes->start << PAGE_SHIFT;
-			max_entries = (nodes->size - pfn) *
-				AMDGPU_GPU_PAGES_IN_CPU_PAGE;
+			max_entries = min((nodes->size - pfn) *
+				AMDGPU_GPU_PAGES_IN_CPU_PAGE, max_entries);
 		} else {
 			addr = 0;
-			max_entries = S64_MAX;
 		}
 
 		if (pages_addr) {
@@ -1729,7 +1729,7 @@ static int amdgpu_vm_bo_split_mapping(struct amdgpu_device *adev,
 			addr += pfn << PAGE_SHIFT;
 		}
 
-		last = min((uint64_t)mapping->last, start + max_entries - 1);
+		last = start + max_entries - 1;
 		r = amdgpu_vm_bo_update_mapping(adev, vm, false, false, resv,
 						start, last, flags, addr,
 						dma_addr, fence);