Interrupt number 100

Question

What is Interrupt 100 used for? I was going through the Qemu translation code qemu/target-i386/translate.c where I saw the reference.

static void gen_interrupt(DisasContext *s, int intno,
                      target_ulong cur_eip, target_ulong next_eip)
{
    if (intno == 100) {
        gen_helper_q_start_trace();         
        return;
    } else if (intno == 101) {
        gen_helper_q_end_trace();
        return;
    } else if (intno == 104 ) {
      gen_helper_q_hypercall_entry();    //Hypercall Entry
      return;
}