load_sp0
PVOP_VCALL1(pv_ops, cpu.load_sp0, sp0);
void (*load_sp0)(unsigned long sp0);
load_sp0(task_top_of_stack(task));
load_sp0((unsigned long)(cpu_entry_stack(cpu) + 1));
.cpu.load_sp0 = native_load_sp0,
pv_ops.cpu.load_sp0 = xen_load_sp0;