[Qemu-devel] CPU TLB flush with multithread TCG.

[Frederic Konrad <fred.konrad@greensocs.com>]

Hi everybody,

In multithread tlb_flush is broken as CPUA can flush an other CPUB and 
CPUB can be
executing code, and fixing this can be quite hard:
   * We need to exit the CPU which is flushed.
   * Makes sure the CPU is stopped.
   * Then we can flush tlb.
The big issues are:
   * Two threads can be doing a flush at the same time.
   * Something can restart the CPU during the flush.

A better idea I think is that instead of flushing tlb we can put a flag 
in CPUState such
as flush_request and ask the cpu to exit.
Then later once the CPU is exited we can flush tlbs if flush_request is set.
It will ensure that the CPU won't execute code as it's associated thread 
will be
flushing.

Can this work?

Thanks,
Fred