drm/amdgpu: Reduce SG bo memory usage for mGPUs

For userptr bo, if adev is not in IOMMU isolation mode, RAM direct map
to GPU, multiple GPUs use same system memory dma mapping address, they
can share the original mem->bo in attachment to reduce dma address array
memory usage.
Signed-off-by: NPhilip Yang <Philip.Yang@amd.com>
Reviewed-by: NFelix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

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

@@ -708,10 +708,12 @@ static int kfd_mem_attach(struct amdgpu_device *adev, struct kgd_mem *mem,
 		pr_debug("\t add VA 0x%llx - 0x%llx to vm %p\n", va,
 			 va + bo_size, vm);
 
-		if (adev == bo_adev || (mem->domain == AMDGPU_GEM_DOMAIN_VRAM &&
-					amdgpu_xgmi_same_hive(adev, bo_adev))) {
-			/* Mappings on the local GPU and VRAM mappings in the
-			 * local hive share the original BO
+		if (adev == bo_adev ||
+		   (amdgpu_ttm_tt_get_usermm(mem->bo->tbo.ttm) && adev->ram_is_direct_mapped) ||
+		   (mem->domain == AMDGPU_GEM_DOMAIN_VRAM && amdgpu_xgmi_same_hive(adev, bo_adev))) {
+			/* Mappings on the local GPU, or VRAM mappings in the
+			 * local hive, or userptr mapping IOMMU direct map mode
+			 * share the original BO
 			 */
 			attachment[i]->type = KFD_MEM_ATT_SHARED;
 			bo[i] = mem->bo;