Re: [Qemu-devel] Re: Two QMP events issues

[Anthony Liguori <anthony@codemonkey.ws>]

On 02/08/2010 08:12 AM, Daniel P. Berrange wrote:
>
> For further backgrou, the key end goal here is that in a QMP client, upon
> receipt of the  'RESET' event, we need to reliably&  immediately determine
> why it  occurred. eg, triggered by watchdog, or by guest OS request. There
> are actually 3 possible sequences
>
>   - WATCHDOG + action=reset, followed by RESET.  Assuming no intervening
>     event can occurr, the client can merely record 'WATCHDOG' and interpret
>     it when it gets the immediately following 'RESET' event
>
>   - RESET, followed by WATCHDOG + action=reset. The client doesn't know
>     the reason for the RESET and can't wait arbitrarily for WATCHDOG since
>     there might never be one arriving.
>
>   - RESET + source=watchdog. Client directly sees the reason
>
> The second scenario is the one I'd like us to avoid at all costs, since it
> will require the client to introduce arbitrary delays in processing events
> to determine cause. The first is slightly inconvenient, but doable if we
> can assume no intervening events will occur, between WATCHDOG and the
> RESET events. The last is obviously simplest for the clients.
>    

I really prefer the third option but I'm a little concerned that we're 
throwing events around somewhat haphazardly.

So let me ask, why does a client need to determine when a guest reset 
and why it reset?

Regards,

Anthony Liguori