Re: [Qemu-devel] latest rc: virtio-blk hangs forever after migration

["Marcin Gibuła" <m.gibula@beyond.pl>]

W dniu 2014-07-18 11:37, Paolo Bonzini pisze:
> Il 18/07/2014 11:32, Marcin Gibuła ha scritto:
>>
>>> 3) the next CPU entry will call kvm_arch_put_registers:
>>>
>>>          if (cpu->kvm_vcpu_dirty) {
>>>              kvm_arch_put_registers(cpu, KVM_PUT_RUNTIME_STATE);
>>>              cpu->kvm_vcpu_dirty = false;
>>>          }
>>
>> But, I don't set cpu->kvm_vcpu_dirty anywhere (?).
>
> Yeah, the next CPU entry will *not* call kvm_arch_put_registers with
> your change.  It will call it with vanilla cpu_synchronize_all_states().

That's because in kvmclock, it's used only to read cpu registers, not 
edit them.

Now, because making this call "invisible" makes it work, I'm speculating 
that following happens:

[migration starts]
kvmclock: calls cpu_synchronize_all_states()
somewhere in qemu: completes IO
somewhere in qemu: calls cpu_synchronize_all_states() <- old state


Is it (or something similar) possible? I didn't dig deep enough into 
internals yet, but perhaps you could point if thats the right direction?

-- 
mg