Re: xl mem-set for domain 0 regression

[James Dingwall <james@dingwall.me.uk>]

On Wed, Oct 11, 2017 at 05:00:45PM +0100, Wei Liu wrote:
> On Tue, Oct 10, 2017 at 04:03:32PM +0100, James Dingwall wrote:
> > Hi,
> > 
> > We are migrating from xen 4.4 to xen 4.8.  At the moment we boot our system
> > with a xen command line that includes "dom0_mem=8192m,min:1728m,max:8192m".
> > We have autoballoon of dom0 disabled in xl.conf and instead call xl mem-set
> > 0 <memory_size> to change the dom0 memory allocation.  (We shrink before
> > starting guest domains and then increase it when all are stopped.)
> > 
> > In xen 4.8.2 the xl mem-set command fails with this error:
> > 
> > # xl mem-set 0 3990
> > libxl: error: libxl.c:4196:libxl_set_memory_target: unable to retrieve
> > domain configuration: No such file or directory
> > cannot set domid 0 dynamic max memory to : 3990
> > 
> > I think it was the following commit that made it necessary to access the
> > configuration file but perhaps for the case domid == 0 this should be
> > skipped?  If it is that simple I could try a patch which includes that test.
> 
> There should be a stub configuration file generated for Dom0.
> 
> Check if there is /var/lib/xen/userdata-d.0.0000-*000.libxl-json ?
> 
> If not, check if xen-init-dom0 service is run?

Ahh... :) That was exactly the issue.  We are not using the default startup scripts so this was not called.  I 
had compared to a Gentoo system where this file was not present (for exactly the same reason).  I shall pay more 
attention to the default scripts to ensure there is nothing else we have missed.

Thanks,

James

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