[pve-devel] qemu2.7: cpu hotplug && hot-unplug v1

Harald Leithner leithner at itronic.at
Thu Sep 8 18:06:55 CEST 2016


Ok thx for the Info.

Am 7. September 2016 11:28:54 MESZ, schrieb Alexandre DERUMIER <aderumier at odiso.com>:
>>>small question to live migration, you wrote the hot plug features
>breaks 
>>>live migration but the qemu wiki says that this should work. 
>
>The wiki is pretty old.
>When I said that it break live migration,It's only if you have already
>enable livemigration on qemu 2.6 and try to migrate to new qemu 2.7
>hotplug system.
>
>I only applied the new hotplug system when the vm is stop/start a first
>time (to have 2.7 machine version running).
>
>So this does not break the migration.
>
>
>Here the last doc for cpu hotplug (the doc is not yet commited in qemu
>git)
>https://lists.gnu.org/archive/html/qemu-devel/2016-08/msg03157.html
>
>----- Mail original -----
>De: "Harald Leithner" <leithner at itronic.at>
>À: "pve-devel" <pve-devel at pve.proxmox.com>
>Envoyé: Mercredi 7 Septembre 2016 09:26:57
>Objet: Re: [pve-devel] qemu2.7: cpu hotplug && hot-unplug v1
>
>Hi, 
>
>small question to live migration, you wrote the hot plug features
>breaks 
>live migration but the qemu wiki says that this should work. 
>The only limitations are: 
>
>1. migration target should be started with initial CPU count '-smp XX' 
>that includes hot-added CPUs on migration source side. 
>2. CPU shouldn't be hot-plugged during migration. 
>adding CPUs should be done in successive order from lower to higher IDs
>
>3. in [0..max-cpus) range. 
>It's possible to add arbitrary CPUs in random order, however that would
>
>cause migration to fail on its target side. 
>
>http://wiki.qemu.org/Features/CPUHotplug 
>
>Or is only the implementation for proxmox limited? 
>
>Harald 
>
>Am 06.09.2016 um 12:41 schrieb Alexandre Derumier: 
>> Hi, 
>> This patch series implement new qemu 2.7 cpu hotplug framework, with
>device_add|device_del 
>> 
>> hot-unplug is working now ! 
>> 
>> config example: 
>> --------------- 
>> cpu: kvm64 
>> sockets:2 
>> cores:2 
>> 
>> generate cmdline 
>> ---------------- 
>> -cpu kvm64,+lahf_lm,+sep,+kvm_pv_unhalt,+kvm_pv_eoi,enforce 
>> -smp 1,sockets=2,cores=2,maxcpus=4 
>> -device kvm64-x86_64-cpu,id=cpu2,socket-id=0,core-id=1,thread-id=0 
>> -device kvm64-x86_64-cpu,id=cpu3,socket-id=1,core-id=0,thread-id=0 
>> -device kvm64-x86_64-cpu,id=cpu4,socket-id=1,core-id=1,thread-id=0 
>> 
>> 
>> First core is not hotpluggable (-smp 1). (socket-id=0,core-id=0) 
>> Others cores are added with -device, with cpumodel,socket-id &&
>core-id. 
>> 
>> cpuflags are defined globally in -cpu , and are auto applied on
>hotplug 
>> 
>> Tested with debian jessie, kernel 3.16. 
>> 
>> This new config is only apply with machine 2.7+cpu hotplug enabled,
>as it break live migration. 
>> 
>> 
>> _______________________________________________ 
>> pve-devel mailing list 
>> pve-devel at pve.proxmox.com 
>> http://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-devel 
>> 
>
>-- 
>Harald Leithner 
>
>ITronic 
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