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Re: [Xen-devel] [PATCH 4/6] xen: don't free percpu areas during suspend


  • To: Jan Beulich <JBeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Juergen Gross <jgross@xxxxxxxx>
  • Date: Wed, 27 Mar 2019 17:52:18 +0100
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  • Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>
  • Delivery-date: Wed, 27 Mar 2019 16:52:25 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Openpgp: preference=signencrypt

On 27/03/2019 17:38, Jan Beulich wrote:
>>>> On 27.03.19 at 17:18, <jgross@xxxxxxxx> wrote:
>> On 27/03/2019 16:55, Andrew Cooper wrote:
>>> On 18/03/2019 13:11, Juergen Gross wrote:
>>>> Instead of freeing percpu areas during suspend and allocating them
>>>> again when resuming keep them. Only free an area in case a cpu didn't
>>>> come up again when resuming.
>>>>
>>>> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
>>>
>>> Hmm - this is slightly problematic, given the dual nature of this code.
>>>
>>> I agree that it this change is beneficial for the suspend case, but it
>>> is a problem when we are parking an individual CPU for smt=0 or
>>> xen-hptool reasons.
>>>
>>> Do we have any hint we can use when taking the CPU down as to whether
>>> we're expecting it to come straight back up again?
>>
>> Did you look into the patch? I did this by testing system_state.
> 
> I think there's a wider problem here: enable_nonboot_cpus()
> only brings back up the CPUs that were previously online.
> Parked ones would be left alone, yet after resume they'd
> need to be put back into parked state.

I can add that handling in the respin of the series.


Juergen

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