Re: [Xen-devel] [PATCH] Fix xm commands for inactive domains

[Ewan Mellor <ewan@xxxxxxxxxxxxx>]

On Wed, Dec 13, 2006 at 05:11:01PM +0000, Daniel P. Berrange wrote:

> On Wed, Dec 13, 2006 at 03:38:09PM +0000, Daniel P. Berrange wrote:
> > 
> > The commands 'mem-set' 'mem-max' and 'vcpu-set' are all broken when used 
> > against an inactive domain. The backend implementation of these commands
> > typically updates the in-memory config held by XenD, and does a hypercall
> > or xenstore write to update the live guest. Obviously the latter part fails
> > with inactive guests. The changes are also not persisted to disk.
> > 
> > The attached patch ensures that the hypercalls/xenstore writes are not
> > tried for inactive guests. It will also write out the changes to disk
> > so config changes to inactive guests are preserved across XenD restarts.
> > 
> > Normally memory_dynamic_min/max  and online_vcpus are picked up from the
> > running domain state. This doesn't apply for inactive guests, so when 
> > changing config for inactive guests, we also update those 3 parameters to
> > match the new settings. 
> > 
> > So, at the end of all this, I can do:
> > 
> > 1. Define an inactive domain...
> > 
> >   # xm new demo
> >   # xm list demo
> >   Name                                      ID   Mem VCPUs      State   
> > Time(s)
> >   demo                                           410     1                 
> > 0.0
> >   # xm list --long demo | grep mem
> >       (memory 410)
> >       (maxmem 800)
> >       (shadow_memory 0)
> >       (memory_dynamic_min 410)
> >       (memory_dynamic_max 800)
> > 
> > 2. Change its memory config...
> > 
> >   # xm mem-set demo 500
> >   # xm mem-max demo 1000
> >   # xm list --long demo | grep mem
> >       (memory 500)
> >       (maxmem 1000)
> >       (shadow_memory 0)
> >       (memory_dynamic_min 500)
> >       (memory_dynamic_max 1000)
> >   # xm list demo
> >   Name                                      ID   Mem VCPUs      State   
> > Time(s)
> >   demo                                           500     1                 
> > 0.0
> > 
> > 3. Change its cpu config...
> > 
> >   # xm vcpu-set demo 8
> >   # xm list --long demo | grep vcpu
> >       (vcpus 8)
> >       (online_vcpus 8)
> >   # xm list demo
> >   Name                                      ID   Mem VCPUs      State   
> > Time(s)
> >   demo                                           500     8                 
> > 0.0
> > 
> > 4. Start it with new settings...
> > 
> >   # xm start demo
> >   # xm list demo
> >   Name                                      ID   Mem VCPUs      State   
> > Time(s)
> >   demo                                      22   500     8     -b----      
> > 0.7
> > 
> > NB, the patch is structured so there is no functional change for active
> > guests, to minimise risk of regression in this 3.0.4 freeze. I think this
> > is really important to get working in 3.0.4 since inactive domain support
> > is of pretty limited usefullness as it currently stands.  Hopefully in 3.0.5
> > the XenAPI will make it possible to change all aspects of an inactive guest
> > config.
> > 
> >   Signed-off-by: Daniel P. Berrange  <berrange@xxxxxxxxxx>
> 
> There was one final problem I've just also fixed - for some reason the
> SEXPR api to change max memory was calling into XenDomain instead of
> XenDomainInfo directly. This meant it needed a domid - which doesn't
> exist in inactive domain case. So this updated version of the patch also
> fixed SrvDomain.py  to call the XenDomainInfo object it already has 
> directly - this matches the style of the rest of the method in SrvDomain.py
> 
> The attached patch contains my original patch + this SrvDomain.py fix.
> Now, not only does 'xm' work correctly, but libvirt can manage inactive
> domains & their config settings too.
> 
>  Signed-off-by: Daniel P. Berrange  <berrange@xxxxxxxxxx>

Applied, thanks Daniel.  Nice stuff.

Ewan.

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