Re: [Qemu-devel] [PULL 26/28] apic: Use apic_id as apic's migration instance_id

[Igor Mammedov]

On Tue, 26 Jul 2016 17:17:47 +0530
Amit Shah <address@hidden> wrote:

> On (Tue) 26 Jul 2016 [10:00:49], Igor Mammedov wrote:
> > On Tue, 26 Jul 2016 10:41:38 +0530
> > Amit Shah <address@hidden> wrote:
> >   
> > > On (Wed) 20 Jul 2016 [12:08:32], Eduardo Habkost wrote:  
> > > > From: Igor Mammedov <address@hidden>
> > > > 
> > > > instance_id is generated by last_used_id + 1 for a given device type
> > > > so for QEMU with 3 CPUs instance_id for APICs is a seti of [0, 1, 2]
> > > > When CPU in the middle is hot-removed and migration started
> > > > APICs with instance_ids 0 and 2 are transferred in migration stream.
> > > > However target starts with 2 CPUs and APICs' instance_ids are
> > > > generated from scratch [0, 1] hence migration fails with error
> > > >   Unknown savevm section or instance 'apic' 2
> > > > 
> > > > Fix issue by manually registering APIC's vmsd with apic_id as
> > > > instance_id, in this case instance_id on target will always
> > > > match instance_id on source as apic_id is the same for a given
> > > > cpu instance.
> > > > 
> > > > Reported-by: Bharata B Rao <address@hidden>
> > > > Signed-off-by: Igor Mammedov <address@hidden>
> > > > Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> > > > Reviewed-by: Michael S. Tsirkin <address@hidden>
> > > > Signed-off-by: Eduardo Habkost <address@hidden>    
> > > 
> > > After these patches, the static checker complains about missing
> > > sections:
> > > 
> > > Section "apic-common" does not exist in dest
> > > Section "apic" does not exist in dest
> > > Section "kvm-apic" does not exist in dest  
> > It works for me, could you post reproducing commands?  
> 
> This was flagged by a nightly run of the static checker when this
> series was pulled.  On a 'before' tree, ie one w/o the patches, do
> this:
> 
> qemu -dump-vmstate before.json
> 
> and for after:
> 
> qemu -dump-vmstate after.json
> 
> then,
> 
> python ./scripts/vmstate-static-checker.py -s before.json -d after.json
I don't think it is valid comparison though, as it compares default PC machines.
In this case it's pc-i440fx-2.6 and pc-i440fx-2.7, you see the difference
which is expected due to instance_id change.

You shouldn't see it when comparing same machine types.
 
> and that shows the output from above.
>
> 
>               Amit