Re: S3 sleep in dom0 breaks dom0<->domU wallclock synchronization

["Jan Beulich" <JBeulich@novell.com>]

>>> On 06.07.10 at 11:10, Joanna Rutkowska <joanna@invisiblethingslab.com> wrote:
> On 07/06/10 05:52, Keir Fraser wrote:
>> On 05/07/2010 23:50, "Jeremy Fitzhardinge" <jeremy@goop.org> wrote:
>> 
>>>> BTW: wouldn't it be good to actually notify them? Consider e.g. DomU
>>>> that has some device assigned to it (say a NIC) -- if we emulated S3
>>>> suspend/resume for this DomU, there is a hope it would properly
>>>> suspend/reinitialize the NIC, wouldn't it?
>>>>   
>>>
>>> I guess?  That implies some kind of PV S3 suspend and resume event to
>>> feed into the dom U's device model.  What does 2.6.18-xen do?
>> 
>> I don't think our S3 support is very compatible with PV device passthrough.
>> We support HVM virtual S3, and can S3-sleep HVM guests across real host S3,
>> but we don't have similar for PV guests.
>> 
> 
> How about implementing something very simple, like a notification via
> xenstore (say, Dom0 would be setting some key)? Interested DomUs could
> then register a watch, and get notified when the system was resumed from
> S3. This would let them e.g. to call whatever hypercall is used normally
> on DomU boot to sync DomU wallclock, or reinitialize/reconnect the NIC.

Wouldn't it be much simpler to not introduce any new logic at all and
just let Dom0 tools/scripts take care of properly suspending
(checkpointing) all (minimally all pv, but I would really think treating
different kinds of guests differently here is unnecessary) guests
before doing a host suspend, as Jeremy had suggested in an earlier
reply?

Jan