Re: [Qemu-devel] [RFC] exec: eliminate ram naming issue as migration

[Igor Mammedov <imammedo@redhat.com>]

On Wed, 7 Feb 2018 07:49:58 +0000
"Tan, Jianfeng" <jianfeng.tan@intel.com> wrote:

> > -----Original Message-----
> > From: Paolo Bonzini [mailto:pbonzini@redhat.com]
> > Sent: Tuesday, February 6, 2018 1:32 AM
> > To: Igor Mammedov
> > Cc: Tan, Jianfeng; qemu-devel@nongnu.org; Jason Wang; Maxime Coquelin;
> > Michael S . Tsirkin
> > Subject: Re: [Qemu-devel] [RFC] exec: eliminate ram naming issue as
> > migration
> > 
> > On 05/02/2018 18:15, Igor Mammedov wrote:  
> > >>>
> > >>> Then we would have both ram block named pc.ram:
> > >>>               Block Name    PSize
> > >>>                       pc.ram     4 KiB
> > >>>       /objects/pc.ram    2 MiB
> > >>>
> > >>> But I assume it's a corner case which not really happen.  
> > >> Yeah, you're right. :/  I hadn't thought of hotplug.  It can happen indeed.  
> > >
> > > perhaps we should fail object_add memory-backend-foo if it resulted
> > > in creating ramblock with duplicate id  
> > 
> > Note that it would only be duplicated with Jianfeng's patch.  So I'm
> > worried that his patch is worse than what we have now, because it may
> > create conflicts with system RAMBlock names are not necessarily
> > predictable.  Right now, -object creates RAMBlock names that are nicely
> > constrained within /object/.  
> 
> So we are trading off between the benefit it takes and the bad effect it brings.
> 
> I'm wondering if the above example is the only failed case this patch leads to, i.e, only there is a ram named "pc.ram" and "/object/pc.ram" in the src VM?
> 
> Please also consider the second option, that adding an alias name for RAMBlock; I'm not a big fan for that one, as it just pushes the problem to OpenStack/Libvirt.
looking at provided CLI examples it's configuration issue on src and dst,
one shall not mix numa and non numa variants.

> Or any other suggestions?
Fix configuration, namely dst side of it (i.e. use the same -m only variant
without -numa as it's on src).

BTW, what are you trying to achieve adding -numa on dst?

> Thanks,
> Jianfeng