Re: [Xen-devel] xl list -l doesn't work for incoming domain

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Mon, Nov 10, 2014 at 12:38:53PM +0000, Ian Campbell wrote:
> On Mon, 2014-11-10 at 12:35 +0000, Wei Liu wrote:
> > On Fri, Nov 07, 2014 at 11:34:33AM -0500, Zhigang Wang wrote:
> > > On 11/07/2014 05:47 AM, Wei Liu wrote:
> > > > On Thu, Nov 06, 2014 at 02:14:42PM -0500, Zhigang Wang wrote:
> > > >> Hi,
> > > >>
> > > >> While doing VM migration, in the destination side:
> > > >>
> > > >>    # xl list -l
> > > >>     libxl: error: libxl.c:6535:libxl_retrieve_domain_configuration: 
> > > >> fail to get domain configuration for domain 7
> > > >>     [
> > > >>         {
> > > >>             "domid": 0,
> > > >>             "config": {
> > > >>                 "c_info": {
> > > >>                     "type": "pv",
> > > >>                     "name": "Domain-0"
> > > >>                 },
> > > >>                 "b_info": {
> > > >>                     "max_memkb": 876544,
> > > >>                     "target_memkb": 876543,
> > > >>                     "sched_params": {
> > > >>     
> > > >>                     },
> > > >>                     "type.pv": {
> > > >>     
> > > >>                     }
> > > >>                 }
> > > >>             }
> > > >>         }
> > > >>     ]
> > > >>  
> > > >>     # xl list
> > > >>     Name                                          ID   Mem VCPUs      
> > > >> State   Time(s)
> > > >>     Domain-0                                       0   856     4     
> > > >> r-----    2758.9
> > > >>     0004fb00000600003f327a843a5f2b72--incoming     7   131     1     
> > > >> --p---       0.0
> > > >>
> > > >> Testing on:
> > > >>
> > > > 
> > > > What's the rune you used to migrate the domain? xl migrate? Why is the
> > > > domain paused?
> > > 
> > > The domain is under migrating, so the destination side it's paused. When 
> > > migration finish,
> > > it will become running.
> > > 
> > > FYI: the domain migration will success.
> > > 
> > 
> > I see. At that point the configuration was not available, yet. After the
> > domain is successfully migrated, the configuration should be available.
> > 
> > I think a domain under construction without domain configuration is a
> > valid state. What do you think?
> 
> Can we write a stub json file at the beginning of migrate receive, a bit
> like we do on create?
> 

No, we don't generate stub for normal domain at the moment.

Whether we should do it or not, it depends on whether we want libxl user
to see incomplete (and certainly incorrect) domain configuration. I
think not, because libxl user doesn't know how to distinguish stub
(invalid) configuration from a valid one.

> Otherwise code like xl list is going to have start special casing
> domains which have no json, which we've tried hard to avoid I think.
> 

From xl's (and other tools on the same level) point of view, that means
invocation of library function fails, which it should always be ready to
cope with.

Wei.

> Ian.

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