I had to code this up as well.  Everything here looks fine.
For most places I had to convert to be thread-aware, I found using a reference to be cleaner.  Didn't hae to append a "[tid]" everywhere.

Example of my current mwait()
bool                                                                                                                                                                                                               

BaseCPU::mwait(ThreadID tid, PacketPtr pkt)                                                                                                                                                                        

{                                                                                                                                                                                                                  

    assert(tid < numThreads);                                                                                                                                                                                      

    AddressMonitor &monitor = addressMonitor[tid];                                                                                                                                                                   
if(monitor.gotWakeup == false) {                                                                                                                                                                                 
    int block_size = cacheLineSize();                                                                                                                                                                            
    uint64_t mask = ~((uint64_t)(block_size - 1));

    assert(pkt->req->hasPaddr());                                                                                                                                                                                
    monitor.pAddr = pkt->getAddr() & mask;                                                                                                                                                                       
    monitor.waiting = true;

    DPRINTF(Mwait,"[tid:%d] mwait called (vAddr=0x%lx, paddr=0x%lx)\n",                                                                                                                                          
            tid, monitor.vAddr, monitor.pAddr);                                                                                                                                                                  
    return true;                                                                                                                                                                                                 
} else {                                                                                                                                                                                                         
    monitor.gotWakeup = false;                                                                                                                                                                                   
    return false;                                                                                                                                                                                                
}

}