align_down
target = align_down(altinsnptr, SZ_4K) + orig_offset;
new_offset = target - align_down(insnptr, SZ_4K);
data_gpa = align_down(data_gpa, backing_src_pagesz);
start_gpa = align_down(start_gpa, alignment);
addr = align_down(addr, host_page_size);
guest_test_phys_mem = align_down(guest_test_phys_mem, host_page_size);
guest_test_phys_mem = align_down(guest_test_phys_mem, 1 << 20);
guest_test_phys_mem = align_down(guest_test_phys_mem, alignment);
vm_vaddr_t seg_vstart = align_down(phdr.p_vaddr, vm->page_size);
args->gpa = align_down(args->gpa, backing_src_pagesz);
args->gpa = align_down(args->gpa, 1 << 20);
start = align_down(memstress_args.gpa, PG_SIZE_1G);
gpa = align_down(gpa, alignment);