[vbox-dev] cpu hotplug support

[Alexander Eichner]

Hi,

1. there is a directory missing in the path, sorry. It must be /sys/ 
devices/system/cpu/cpu<id>

2. yes :)

Regards,
Alexander Eichner

Alexey Eremenko wrote:

> On Thu, Apr 22, 2010 at 5:29 AM, Alexander Eichner
> <Alexander.Eichner at sun.com> wrote:
>> Hi,
>>
>> any recent Linux kernel should support it. I used Ubuntu 9.10.  
>> Windows is
>> also supported but Windows Server 2008 R2 x64 Datacenter edition
>> implements CPU hot-add only.
>>
>> The following commands configure the VM for CPU hotplugging:
>>
>> Configuration:
>>
>> VBoxManage modifyvm name --cpuhotplug on -- switches CPu hot- 
>> plugging on
>>
>> VBoxManage modifyvm name --cpus <nr> -- sets the maximum number of  
>> CPus the
>> VM can have
>>
>> VBoxManage modifyvm name --plugcpu <id> -- Adds the CPU with <id>  
>> to the VM
>> while it is off
>>
>> VBoxManage modifyvm name --unplugcpu <id> -- Removes the CPU with  
>> <id> from
>> the VM while it is off, CPU 0 can't be removed.
>>
>>
>>
>> Initiating hot-add/hot-remove events:
>>
>> VBoxManage controlvm name plugcpu <id> -- Adds CPU <id> while the  
>> VM is
>> running
>>
>> VBoxManage controlvm name unplugcpu <id> -- Removes CPU <id> while  
>> the VM is
>> running.
>>
>>
>> Linux doesn't make use of new CPUs by default. You either need to  
>> update the
>> guest additions which includes a service handling the events.
>> If you don't want to update the guest additions you can also  
>> execute the
>> following command as root:
>>
>> echo 1 > /sys/devices/cpus/cpu<id>/online
>>
>> To eject a CPU without installed guest additions you have to do the
>> following before actually ejecting the CPU:
>>
>> echo 1 > /sys/devices/LNXSYSTEM:00/device:00/ACPI0004:<i>/ 
>> LNXCPU:<i2>/eject
>>
>> The <i> and <i2> numbers don't need to be equal and they do not  
>> match the
>> <id> value used to enable a CPU. So you have to search for the  
>> right CPU
>> object unfortunately.
>> The reason behind is to prevent ejection of CPUs while the guest  
>> may still
>> use them. The above command will tell the kernel to disable the CPU.
>>
>
> hmm...
>
> Using Mandriva Linux 2010 guest OS. (kernel 2.6.31)
> I don't have "cpus" folder under: "/sys/devices/..."
>
> 1. any ideas?
>
> 2. First email was co-sent by "Alexander Eichner" and "Sebastian
> Dyroff"... Does it mean Alex studying in "TU-Berlin" and also works at
> Oracle ?
>
> -- 
> -Alexey Eromenko "Technologov"
>
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