Re: [Xen-devel] "xl vcpu-set" not persistent across reboot?

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Jun 06, 2016 at 02:07:46PM +0100, Stefano Stabellini wrote:
> On Mon, 6 Jun 2016, Jan Beulich wrote:
> > >>> On 03.06.16 at 18:35, <wei.liu2@xxxxxxxxxx> wrote:
> > > I got a patch ready.  But QEMU upstream refuses to start on the receiving 
> > > end
> > > with following error message:
> > > 
> > > qemu-system-i386: Unknown savevm section or instance 'cpu_common' 1
> > > qemu-system-i386: load of migration failed: Invalid argument
> > > 
> > > With QEMU traditional HVM guest and PV guest, the guest works fine -- up
> > > and running with all hot plugged cpus available.
> > > 
> > > So I think the relevant libxl information is transmitted but we also
> > > need to fix QEMU upstream. But that's a separate issue.
> 
> For clarity, you have applied the patch below, started a VM, hotplugged
> a vcpu, rebooted the guest, then migrated the VM, but at this point
> there is an error?
> 

Apply this patch, start a guest, hotplug some cpus, make them online
inside guest, and xl migrate guest localhost.

You will see this in qemu log.

> What are the QEMU command line arguments at the receiving side? Are you
> sure that the increased vcpu count is passed to the receiving end by
> libxl? It looks like QEMU has been started passing the old vcpu count as
> command line argument (-smp etc) at the receiving end.
> 

The QEMU command line should be the same on the sending side.

The -smp 1,maxvcpus=4 (something like that).

Does that mean we need to somehow alter QEMU's command line?

Wei.

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