Re: [Qemu-devel] [PATCH v2 1/2] hw/net: add support for Allwinner EMAC Fast Ethernet controller

[Peter Crosthwaite]

On Wed, Jan 15, 2014 at 8:25 PM, Juan Quintela <address@hidden> wrote:
> Peter Crosthwaite <address@hidden> wrote:
>
>> But is the saved link state meaningful? The fact that net is not
>> migrating means that this link_ok migrated variable is potentially
>> incoherent with the net layer. E.G. What happens in the following
>> case:
>>
>> Run QEMU
>> Link is Good
>> Save
>>
>> Run Again
>> Link is bad
>> Load
>>
>> The loaded emulation will have link_ok due to the vmsd load despite
>> the link being down in the new net layer environment. It will not
>> correct until net-layer activity causes a ->link_state_changed
>> callback.
>>
>> Can this be just solved cleanly by calling the mii_set_link fn (added
>> in this patch) always on post load and removing this link_ok state?
>> This will mean that guest will see a link state transition immediately
>> on load if the link state changes from the saved-machine state to the
>> loaded-machine state.
>
> You can do that on post-load, but the problem is that when you run
> post-load, the guest is not running yet on destination, so you need to
> be careful about what functions do you use.
>

Ok,

But in this case the guest visible side effect is just register state
change. There is no transitional event to worry about. I guess in the
case where a link state transition can cause an interrupt it could get
complicated?

Regards,
Peter

> Later, Juan.
>