Re: [Qemu-ppc] [Qemu-devel] [PULL 095/107] spapr: clock should count only if vm is running

[Mark Cave-Ayland]

On 02/02/17 09:13, Laurent Vivier wrote:

> On 02/02/2017 09:37, Mark Cave-Ayland wrote:
>> On 02/02/17 05:14, David Gibson wrote:
>>
> ...
>> Hi David/Laurent,
> 
> Hi Mark,
> 
>> I just noticed this in your pull request today - this looks like it is
>> along similar lines to the prototype patch I proposed last year as part
>> of the decrementer migration thread discussion, i.e. use a
>> vm_change_state_handler() to sync the clock on pause/resume.
>>
>> Am I right in thinking this now solves the timebase migration problem,
>> and so the only part required is to encode the decrementer relative to
>> the timebase during migration to ensure its value is also migrated
>> correctly?
> 
> Do you have a link to this thread discussion?
> 
> The main purpose of this patch was only to stop the clock (TBR) while
> the machine is paused, so I'd like to know what is the problem you are
> speaking about.

Hi Laurent,

Yes indeed. The discussion spanned a couple of threads last year, but
the start of it was my patch to migrate the decrementer to fix an issue
I was seeing when migrating Darwin images on the Mac machines under TCG:

https://lists.gnu.org/archive/html/qemu-devel/2016-01/msg00544.html

This then eventually became a separate thread here:

https://lists.gnu.org/archive/html/qemu-devel/2016-01/msg04622.html


ATB,

Mark.