VMEM_CROSS_P
KASSERT(!VMEM_CROSS_P(phase, phase + size - 1, nocross));
if (VMEM_CROSS_P(phase, phase + sz - 1,
if (VMEM_CROSS_P(start, start + size - 1, nocross)) {
KASSERT(!VMEM_CROSS_P(start, start + size - 1, nocross));