On 9/11/2020 1:53 PM, Dr. David Alan Gilbert wrote:
> * Steve Sistare (steven.sist...@oracle.com) wrote:
>> After cprload, the guest console misbehaves. You must type 8 characters
>> before any are echoed to the terminal. Qemu was not sending interrupts
>> to the guest because the QEMU_CLOCK_VIRTUAL timers_state.cpu_clock_offset
>> was bad. The offset is usually updated at cprsave time by the path
>>
>> save_cpr_snapshot()
>> vm_stop()
>> do_vm_stop()
>> if (runstate_is_running())
>> cpu_disable_ticks();
>> timers_state.cpu_clock_offset = cpu_get_clock_locked();
>>
>> However, if the guest is in RUN_STATE_SUSPENDED, then cpu_disable_ticks is
>> not called. Further, the earlier transition to suspended in
>> qemu_system_suspend did not disable ticks. To fix, call cpu_disable_ticks
>> from save_cpr_snapshot.
>>
>> Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
>
> Are you saying this is really a more generic bug with migrating when
> suspended and we should fix this anyway?
Yes. Or when suspended and calling save_vmstate(), or
qmp_xen_save_devices_state().
Each of those functions needs the same fix unless someone identifies a more
centralized way in the state transition logic to disable ticks.
- Steve
>> ---
>> migration/savevm.c | 5 +++++
>> 1 file changed, 5 insertions(+)
>>
>> diff --git a/migration/savevm.c b/migration/savevm.c
>> index f101039..00f493b 100644
>> --- a/migration/savevm.c
>> +++ b/migration/savevm.c
>> @@ -2729,6 +2729,11 @@ void save_cpr_snapshot(const char *file, const char
>> *mode, Error **errp)
>> return;
>> }
>>
>> + /* Update timers_state before saving. Suspend did not so do. */
>> + if (runstate_check(RUN_STATE_SUSPENDED)) {
>> + cpu_disable_ticks();
>> + }
>> +
>> vm_stop(RUN_STATE_SAVE_VM);
>>
>> ret = qemu_savevm_state(f, op, errp);
>> --
>> 1.8.3.1
>>
