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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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.

Jan



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