On 07/08/2009 10:53, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>> 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.
So what does improving ticket lock behaviour have to do with save/restore?
I'm a bit confused now.
> 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).
I'll certainly consider the patch. I'd also consider a CPUID flag to
indicate its presence.
 -- Keir
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