On 18/07/2013 17:35, Paolo Bonzini wrote:
Il 18/07/2013 17:06, Peter Maydell ha scritto:
On 18 July 2013 16:02,<fred.kon...@greensocs.com> wrote:
As I said in the last email, we have issues with determinism with icount.
We are wondering if determinism is really ensured with icount?
My opinion is that it *should* be deterministic but it would
be unsurprising if the determinism had got broken along the way.
First of all, it can only be deterministic if the guest satisfies (at
least) all the following condition:
1) only uses timer that QEMU bases on vm_clock (which means that you
should use "-rtc clock=vm"---sorry Fred, didn't think about this in the
previous answer);
2) never does any network operation nor any asynchronous disk I/O operation
3) never halts the VCPU waiting for an interrupt
Hi,
qemu_alarm is making the replay not deterministic too.
We tried to remove those alarms and it seems to replay well (at least
far better).
So the question is: how we can solve that?
We thought at two possibilities :
* record/replay them, like IO.
* base them on our new ic_clock.
Both have drawbacks:
* record/replay won't make icount more deterministic (run to run).
* ic_clock speed time is apparently not constant.
Thanks,
Fred
