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

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
destroy the original vcpu and start the new one. My point is that
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.
the hypervisor you have to trap feature registers and other
implementation defined registers to show the same value across all
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.


Julien Grall

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