On Thu, 2016-09-22 at 12:24 +0100, Julien Grall wrote: > On 22/09/16 09:43, Dario Faggioli wrote: > > Local migration basically --from the vcpu perspective-- means > > create a > > new vcpu, stop the original vcpu, copy the state from original to > > new, > > destroy the original vcpu and start the new one. My point is that > > this > > is not something that can be done within nor initiated by the > > scheduler, e.g., during a context switch or a vcpu wakeup! > > By local migration, I meant from the perspective of the hypervisor. > In > the hypervisor you have to trap feature registers and other > implementation defined registers to show the same value across all > the > physical CPUs. > You mean we trap feature registers during the (normal) execution of a vcpu, because we want Xen to vet what's returned to the guest itself. And that migration support, and hence the possibility that the guest have been migrated to a cpu different than the one where it was created, is already one of the reasons why this is necessary... right?
If yes, and if that's "all" we need, I think it should be fine. > You don't need to recreate the vCPU every time you move from one set > of > CPUs to another one. Sorry for the confusion. > No, I am sorry... it's not you that you're making confusion, it's probably me knowing to few about ARM, and did not think at the above when you said "migration". :-) Regards, Dario -- <<This happens because I choose it to happen!>> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)
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