On 03/02/2015 17:17, Richard Henderson wrote:
>> > @@ -759,7 +760,9 @@ static void page_flush_tb_1(int level, void **lp)
>> > PageDesc *pd = *lp;
>> >
>> > for (i = 0; i < V_L2_SIZE; ++i) {
>> > - pd[i].first_tb = NULL;
>> > + for (j = 0; j < MAX_CPUS; j++) {
>> > + pd[i].first_tb[j] = NULL;
>> > + }
>> > invalidate_page_bitmap(pd + i);
>> > }
>> > } else {
> Surely you've got to do some locking somewhere in order to be able to modify
> another thread's cpu tb list.
But that's probably not even necessary. page_flush_tb_1 is called from
tb_flush, which in turn is only called in very special circumstances.
It should be possible to have something like the kernel's "stop_machine"
that does the following:
1) schedule a callback on all TCG CPU threads
2) wait for all CPUs to have reached that callback
3) do tb_flush on all CPUs, while it knows they are not holding any lock
4) release all TCG CPU threads
With one TCG thread, just use qemu_bh_new (hidden behind a suitable API
of course!). Once you have multiple TCG CPU threads, loop on all CPUs
with the same run_on_cpu function that KVM uses.
Paolo
