drm/amdkfd: Share the original BO for GTT mapping

If mGPUs is on same IOMMU group, or is ram direct mapped, then mGPUs
can share the original BO for GTT mapping dma address, without creating
new BO from export/import dmabuf.
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/amdgpu/amdgpu_amdkfd_gpuvm.c

@@ -866,9 +866,10 @@ static int kfd_mem_attach(struct amdgpu_device *adev, struct kgd_mem *mem,
 
 		if ((adev == bo_adev && !(mem->alloc_flags & KFD_IOC_ALLOC_MEM_FLAGS_MMIO_REMAP)) ||
 		    (amdgpu_ttm_tt_get_usermm(mem->bo->tbo.ttm) && reuse_dmamap(adev, bo_adev)) ||
-			same_hive) {
+		    (mem->domain == AMDGPU_GEM_DOMAIN_GTT && reuse_dmamap(adev, bo_adev)) ||
+		    same_hive) {
 			/* Mappings on the local GPU, or VRAM mappings in the
-			 * local hive, or userptr mapping can reuse dma map
+			 * local hive, or userptr, or GTT mapping can reuse dma map
 			 * address space share the original BO
 			 */
 			attachment[i]->type = KFD_MEM_ATT_SHARED;