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Subject: Re: [PATCH v2 3/5] locking/qspinlock: Introduce CNA into the slow
 path of qspinlock
To:     Alex Kogan <alex.kogan@oracle.com>,
        Peter Zijlstra <peterz@infradead.org>
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From:   Waiman Long <longman@redhat.com>
Organization: Red Hat
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Date:   Thu, 6 Jun 2019 11:32:46 -0400
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On 6/6/19 11:21 AM, Alex Kogan wrote:
>>> Also, the paravirt code is under arch/x86, while CNA is generic (not
>>> x86-specific).  Do you still want to see CNA-related patching residing
>>> under arch/x86?
>>>
>>> We still need a config option (something like NUMA_AWARE_SPINLOCKS) to
>>> enable CNA patching under this config only, correct?
>> There is the static_call() stuff that could be generic; I posted a new
>> version of that today (x86 only for now, but IIRC there's arm64 patches
>> for that around somewhere too).
> The static_call technique appears as the more desirable long-term approach, but I think it would be prudent to keep the patches decoupled for now so we can move forward with less entanglements.
> So unless anyone objects, we will work on plugging into the existing patching for pv.
> And we will keep that code under arch/x86, but will be open for any suggestion to move it elsewhere.
>
If you mean making the CNV code depends on PARAVIRT_SPINLOCKS for now,
that is fine. The code should be under kernel/locking. You shouldn't put
it somewhere under arch/x86.

-Longman