[Qemu-devel] VM id

[Qemu-devel] VM id

[Gary Jordan]

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Does Qemu have a VM id allocated for each VM?  I did not find this Id in
qemu. HOW deos qemu identify each VM, using thread Id or some other
identifiers?

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Re: [Qemu-devel] VM id

[Eric Blake]

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On 07/02/2014 01:20 PM, Gary Jordan wrote:
> Does Qemu have a VM id allocated for each VM?  I did not find this Id in
> qemu. HOW deos qemu identify each VM, using thread Id or some other
> identifiers?

Each qemu process manages exactly one VM, so qemu doesn't care what id a
guest has.  Higher-level management software, such as libvirt, has
notions of a VM name and UUID (both of which can be specified on the
command line parameters given to qemu, and the UUID can even be
propagated to the guest, such as by SMBIOS readable by dmidecode in the
guest), as well as a VM id (in libvirt's case, a sequentially increasing
number for each VM that libvirt spawns a qemu process for).  But that's
getting outside the realm of qemu, since qemu doesn't care what name or
uuid you picked, only whether you have access to the monitor of the qemu
process.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] VM id

[Gary Jordan]

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If I open two session in a migration operation, how does the qemu know
which one should be accepted? I saw there was a ram_list to check, but no
id of the guest.


2014-07-02 17:59 GMT-04:00 Eric Blake <eblake@redhat.com>:

> On 07/02/2014 01:20 PM, Gary Jordan wrote:
> > Does Qemu have a VM id allocated for each VM?  I did not find this Id in
> > qemu. HOW deos qemu identify each VM, using thread Id or some other
> > identifiers?
>
> Each qemu process manages exactly one VM, so qemu doesn't care what id a
> guest has.  Higher-level management software, such as libvirt, has
> notions of a VM name and UUID (both of which can be specified on the
> command line parameters given to qemu, and the UUID can even be
> propagated to the guest, such as by SMBIOS readable by dmidecode in the
> guest), as well as a VM id (in libvirt's case, a sequentially increasing
> number for each VM that libvirt spawns a qemu process for).  But that's
> getting outside the realm of qemu, since qemu doesn't care what name or
> uuid you picked, only whether you have access to the monitor of the qemu
> process.
>
> --
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>
>

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Re: [Qemu-devel] VM id

[Eric Blake]

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On 07/02/2014 06:29 PM, Gary Jordan wrote:

[please don't top-post on technical lists]

> If I open two session in a migration operation, how does the qemu know
> which one should be accepted? I saw there was a ram_list to check, but no
> id of the guest.

I suggest using higher level software, like libvirt, to manage your
migrations.  The recipient qemu must have the same command line setup as
the sending side, and it is up to you (or your management app) to make
sure you are connecting to the correct port.  As I said before, qemu is
only concerned about a single guest, so as soon as you are involving
multiple qemu processes, you need a higher level application to keep
things straight.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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