nvkm_mmu_heap
heap = nvkm_mmu_heap(mmu, NVKM_MEM_HOST, ~0ULL);
heapM = nvkm_mmu_heap(mmu, heap, sizeM << NVKM_RAM_MM_SHIFT);
heapN = nvkm_mmu_heap(mmu, heap, sizeN << NVKM_RAM_MM_SHIFT);
heapU = nvkm_mmu_heap(mmu, heap, sizeU << NVKM_RAM_MM_SHIFT);