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

[Harald Leithner]

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.
>
>
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>

-- 
Harald Leithner

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