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Re: [Xen-devel] [PATCH v9] new config option vtsc_tolerance_khz to avoid TSC emulation


  • To: Jan Beulich <JBeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Ian Jackson <ian.jackson@xxxxxxxxxx>
  • From: George Dunlap <george.dunlap@xxxxxxxxxx>
  • Date: Mon, 1 Oct 2018 14:38:23 +0100
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  • Cc: Lars Kurth <lars.kurth@xxxxxxxxxx>, Olaf Hering <olaf@xxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>, Marek Marczykowski <marmarek@xxxxxxxxxxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxx, Julien Grall <julien.grall@xxxxxxx>
  • Delivery-date: Mon, 01 Oct 2018 13:38:30 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Openpgp: preference=signencrypt

On 10/01/2018 12:25 PM, Jan Beulich wrote:
>>>> On 01.10.18 at 12:52, <ian.jackson@xxxxxxxxxx> wrote:
>> Olaf Hering writes ("Re: [PATCH v9] new config option vtsc_tolerance_khz to 
>> avoid TSC emulation"):
>>> Am Thu, 13 Sep 2018 09:39:13 +0200
>>> schrieb Olaf Hering <olaf@xxxxxxxxx>:
>>>> this patch was not applied yet, even after a few "pings".
>>>
>>> No reaction since months.
>>> So scrap that patch, just in case it is still part of someones to-consider 
>> queue.
>>
>> I think it would be worth exploring whether this patch could be
>> applied without an explicit ack from Andrew.
>>
>> I confess I ignored all the previous mails because they all started
>>    Andrew,
>> or
>>    Andrew, Lars,
>> so I assumed that you didn't want attention from other
>> maintainers/committers.
>>
>> Now that I look at the thread it is difficult for me to see the wood
>> for the trees but I don't see unanswered concerns.
> 
> Problem is - discussion around this was (iirc) happening not only on
> the list, but also on irc (including perhaps private chats). It was for
> that reason that I made my R-b conditional upon Andrew at least
> giving an informal go-ahead (otherwise, together with Wei's R-b,
> the patch could have gone in).
> 
> Besides the question of correctness from the perspective of guests
> (which imo is not a problem as the feature needs to be actively
> enabled, and I think we have no reason to keep admins from
> breaking their guests if they really mean to), 

I agree with this, BTW.

> I think the main concern
> was with the way migration of the new value was implemented. But I
> really have to defer to Andrew for that, irrespective of him not
> having responded (on the list) to prior pings.

Is Andrew really the only person who knows enough about migration to
give this the thumbs-up?  Technically migration is in the toolstack, and
so Wei should have double-checked that before giving his review; and
when a question was raised, Wei (as the relevant maintainer who had
given it an R-b) should either have asserted that the code was indeed
correct, or withdrawn his R-b and given Olaf feedback to allow him to
get it into shape.

(This is all based on the history sketched out by Jan above; if there is
more to it then of course this analysis may not be correct.)

I was only skimming the thread, and intended to weigh in at some point;
but I didn't really understand why it was blocked on Andrew in the first
place.

 -George

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