handle_syscall
int (*handle_syscall)(struct kvm_vcpu *vcpu);
ret = kvm_mips_callbacks->handle_syscall(vcpu);
.handle_syscall = kvm_trap_vz_no_handler,
extern void handle_syscall(struct uml_pt_regs *regs);
handle_syscall(regs);
handle_syscall(regs);
.test_func = handle_syscall,
.test_func = handle_syscall,