Re: x86: kvm: Revert "remove sched notifier for cross-cpu migrations"

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2015-03-25 12:08+0100, Radim Krčmář:
> Reverting the patch protects us from any migration, but I don't think we
> need to care about changing VCPUs as long as we read a consistent data
> from kvmclock.  (VCPU can change outside of this loop too, so it doesn't
> matter if we return a value not fit for this VCPU.)
> 
> I think we could drop the second __getcpu if our kvmclock was being
> handled better;  maybe with a patch like the one below:

The second __getcpu is not neccessary, but I forgot about rdtsc.
We need to either use rtdscp, know the host has synchronized tsc, or
monitor VCPU migrations.  Only the last one works everywhere.
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