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Subject: Re: [PATCH v12 04/11] kvm/x86: remove kvm memblock dependency
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     Pavel Tatashin <pasha.tatashin@oracle.com>,
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From:   Paolo Bonzini <pbonzini@redhat.com>
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Date:   Fri, 6 Jul 2018 12:08:17 +0200
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On 06/07/2018 11:45, Thomas Gleixner wrote:
>> One possibility is to introduce another layer of indirection: in
>> addition to the percpu pvclock data, add a percpu pointer to the pvclock
>> data and initialize it to point to a page-aligned variable in BSS.  CPU0
>> (used by vDSO) doesn't touch the pointer and keeps using the BSS
>> variable, APs instead redirect the pointer to the percpu data.
> Yeah, thought about that, but the extra indirection is ugly. Instead of
> using per cpu data, I just can allocate the memory _after_ the allocators
> are up and running and use a single page sized static __initdata for the
> early boot.

Either works for me.  Assembly-wise, the indirection should be more or
less the same as what we have now; even more efficient because it
accesses a percpu pointer instead of computing it based on
smp_processor_id().

Paolo