Re: [PATCH 1/2] KVM: take kvm_lock for hardware_disable() during cpu hotplug

[Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>]

(2010/11/18 14:45), Zachary Amsden wrote:

>>> No, I believe your patch is correct and the lock should be there. Did you test with spinlock debugging just to be sure?
>>>
>>
>> Sorry but no.
>>
>> I have no experience with cpu hotplug.
>>
>> So I thought it would take too much time to do real test by myself and reported like this this time.
>>
>> Any easy way to test?
>
> Yes, quite easy. Some systems may not let cpu0 go offline, but you can manually disable and re-enable the other processors:
>
> [root@mysore ~]# echo "0" > /sys/devices/system/cpu/cpu1/online
> [root@mysore ~]# echo "1" > /sys/devices/system/cpu/cpu1/online
>
> Cheers,
>
> Zach


Thanks a lot!

I tried and got a log like this:

kernel: [  422.084620] kvm: disabling virtualization on CPU1
kernel: [  422.085757] CPU 1 is now offline
kernel: [  422.085766] lockdep: fixing up alternatives.
kernel: [  422.085780] SMP alternatives: switching to UP code
kernel: [  472.081069] lockdep: fixing up alternatives.
kernel: [  472.081080] SMP alternatives: switching to SMP code
kernel: [  472.099182] Booting Node 0 Processor 1 APIC 0x1
kernel: [  422.104799] kvm: enabling virtualization on CPU1

Working correctly, I think.


   Takuya