[Qemu-devel] Unable to add ram object with same ID after addition, migration and removal at the target

[Qemu-devel] Unable to add ram object with same ID after addition, migration and removal at the target

[Bharata B Rao]

Hi,

- Add ram object and dimm device at the source

(qemu) object_add memory-backend-ram,id=ram0,size=128M
(qemu) device_add pc-dimm,id=dimm0,memdev=ram0

- Migrate the VM and remove the dimm device and ram object at the target

(qemu) device_del dimm0
(qemu) object_del ram0

- Adding the ram object with same id now at the target fails like this:

(qemu) info memdev

(qemu) object_add memory-backend-ram,id=ram0,size=128M
Duplicate ID 'ram0' for object

Same behaviour is seen on x86 and Power. The problem isn't seen if
migration isn't involved (add, remove, add at the source itself).

Regards,
Bharata.
-- 
http://raobharata.wordpress.com/

Re: [Qemu-devel] Unable to add ram object with same ID after addition, migration and removal at the target

[Dr. David Alan Gilbert]

* Bharata B Rao (bharata.rao@gmail.com) wrote:
> Hi,
> 
> - Add ram object and dimm device at the source
> 
> (qemu) object_add memory-backend-ram,id=ram0,size=128M
> (qemu) device_add pc-dimm,id=dimm0,memdev=ram0
> 
> - Migrate the VM and remove the dimm device and ram object at the target
> 
> (qemu) device_del dimm0
> (qemu) object_del ram0
> 
> - Adding the ram object with same id now at the target fails like this:
> 
> (qemu) info memdev
> 
> (qemu) object_add memory-backend-ram,id=ram0,size=128M
> Duplicate ID 'ram0' for object
> 
> Same behaviour is seen on x86 and Power. The problem isn't seen if
> migration isn't involved (add, remove, add at the source itself).

Is this the same as the one Michael Roth posted a fix for a few days
back; 'monitor: fix object_del for command-line-created objects'

https://lists.gnu.org/archive/html/qemu-devel/2016-11/msg05479.html

Dave

> Regards,
> Bharata.
> -- 
> http://raobharata.wordpress.com/
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] Unable to add ram object with same ID after addition, migration and removal at the target

[Bharata B Rao]

On Fri, Dec 2, 2016 at 11:46 PM, Dr. David Alan Gilbert <dgilbert@redhat.com
> wrote:

> * Bharata B Rao (bharata.rao@gmail.com) wrote:
> > Hi,
> >
> > - Add ram object and dimm device at the source
> >
> > (qemu) object_add memory-backend-ram,id=ram0,size=128M
> > (qemu) device_add pc-dimm,id=dimm0,memdev=ram0
> >
> > - Migrate the VM and remove the dimm device and ram object at the target
> >
> > (qemu) device_del dimm0
> > (qemu) object_del ram0
> >
> > - Adding the ram object with same id now at the target fails like this:
> >
> > (qemu) info memdev
> >
> > (qemu) object_add memory-backend-ram,id=ram0,size=128M
> > Duplicate ID 'ram0' for object
> >
> > Same behaviour is seen on x86 and Power. The problem isn't seen if
> > migration isn't involved (add, remove, add at the source itself).
>
> Is this the same as the one Michael Roth posted a fix for a few days
> back; 'monitor: fix object_del for command-line-created objects'
>
> https://lists.gnu.org/archive/html/qemu-devel/2016-11/msg05479.html
>

Yes, this is same as above, I hadn't noticed Michael's fix.

Will be good to have this fix in 2.8.

Regards,
Bharata.

Re: [Qemu-devel] Unable to add ram object with same ID after addition, migration and removal at the target

[Michael Roth]

Quoting Bharata B Rao (2016-12-04 21:51:32)
> On Fri, Dec 2, 2016 at 11:46 PM, Dr. David Alan Gilbert <dgilbert@redhat.com>
> wrote:
> 
>     * Bharata B Rao (bharata.rao@gmail.com) wrote:
>     > Hi,
>     >
>     > - Add ram object and dimm device at the source
>     >
>     > (qemu) object_add memory-backend-ram,id=ram0,size=128M
>     > (qemu) device_add pc-dimm,id=dimm0,memdev=ram0
>     >
>     > - Migrate the VM and remove the dimm device and ram object at the target
>     >
>     > (qemu) device_del dimm0
>     > (qemu) object_del ram0
>     >
>     > - Adding the ram object with same id now at the target fails like this:
>     >
>     > (qemu) info memdev
>     >
>     > (qemu) object_add memory-backend-ram,id=ram0,size=128M
>     > Duplicate ID 'ram0' for object
>     >
>     > Same behaviour is seen on x86 and Power. The problem isn't seen if
>     > migration isn't involved (add, remove, add at the source itself).
> 
>     Is this the same as the one Michael Roth posted a fix for a few days
>     back; 'monitor: fix object_del for command-line-created objects'
> 
>     https://lists.gnu.org/archive/html/qemu-devel/2016-11/msg05479.html
> 
> 
> Yes, this is same as above, I hadn't noticed Michael's fix.
> 
> Will be good to have this fix in 2.8.

I considered shooting for 2.8, but since it's only triggerable with HMP
(QMP doesn't use the QemuOpts-based parsing so it doesn't hit the
duplicate ID error, so libvirt in turn would be uneffected), and doesn't
seem to be a regression (AFAICT it's been an issue since object_del was
introduced), I figured it could wait till 2.9/2.8.1.

Definitely a pain for testing though...

> 
> Regards,
> Bharata.

Re: [Qemu-devel] Unable to add ram object with same ID after addition, migration and removal at the target

[David Gibson]

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On Mon, Dec 05, 2016 at 12:44:53AM -0600, Michael Roth wrote:
> Quoting Bharata B Rao (2016-12-04 21:51:32)
> > On Fri, Dec 2, 2016 at 11:46 PM, Dr. David Alan Gilbert <dgilbert@redhat.com>
> > wrote:
> > 
> >     * Bharata B Rao (bharata.rao@gmail.com) wrote:
> >     > Hi,
> >     >
> >     > - Add ram object and dimm device at the source
> >     >
> >     > (qemu) object_add memory-backend-ram,id=ram0,size=128M
> >     > (qemu) device_add pc-dimm,id=dimm0,memdev=ram0
> >     >
> >     > - Migrate the VM and remove the dimm device and ram object at the target
> >     >
> >     > (qemu) device_del dimm0
> >     > (qemu) object_del ram0
> >     >
> >     > - Adding the ram object with same id now at the target fails like this:
> >     >
> >     > (qemu) info memdev
> >     >
> >     > (qemu) object_add memory-backend-ram,id=ram0,size=128M
> >     > Duplicate ID 'ram0' for object
> >     >
> >     > Same behaviour is seen on x86 and Power. The problem isn't seen if
> >     > migration isn't involved (add, remove, add at the source itself).
> > 
> >     Is this the same as the one Michael Roth posted a fix for a few days
> >     back; 'monitor: fix object_del for command-line-created objects'
> > 
> >     https://lists.gnu.org/archive/html/qemu-devel/2016-11/msg05479.html
> > 
> > 
> > Yes, this is same as above, I hadn't noticed Michael's fix.
> > 
> > Will be good to have this fix in 2.8.
> 
> I considered shooting for 2.8, but since it's only triggerable with HMP
> (QMP doesn't use the QemuOpts-based parsing so it doesn't hit the
> duplicate ID error, so libvirt in turn would be uneffected), and doesn't
> seem to be a regression (AFAICT it's been an issue since object_del was
> introduced), I figured it could wait till 2.9/2.8.1.
> 
> Definitely a pain for testing though...

How complex is the fix?  If it's simple, then AIUI we can still put
real bugfixes like this into 2.8.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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