Re: [Xen-devel] resume of HVM guest without PV drivers

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 07.08.09 11:44 >>>
>So you're interested in a scenario that is PV'ed-up enough to do hypercalls,
>but not enough to talk xenbus?

Yes - right now the main goal is to improve ticket lock behavior.

>If you only care about being able to poll for having migrated/saved, there
>must be some other bit of state you can push to Xen that doesn't get
>migrated/saved. Like, create an IPI event channel and poll its status
>(EVTCHNOP_status).

No, a hypercall of any sort is not a good option (namely if I wanted to
use a hypercall page, which I'm not certain about yet, as that would
create a chicken-and-egg problem). It must be some memory state that
I can examine.

And with the goal of improving lock behavior, I also definitely will need to
have a way to know whether a remote vCPU is currently running, and
here it is obviously preferable to not have to use a hypercall to find out
(i.e. I'd want the runstate area change I'm looking at anyway).

Jan


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