Re: [Xen-devel] [RFC 0/5] xen/arm: support big.little SoC

[Julien Grall <julien.grall@xxxxxxx>]

Hi Dario,

On 22/09/16 17:31, Dario Faggioli wrote:
> 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?
That's correct.

Regards,

--
Julien Grall

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