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 11:33), Zachary Amsden wrote:
> On 11/17/2010 04:04 PM, Takuya Yoshikawa wrote:
>> (2010/11/18 10:59), Zachary Amsden wrote:
>>> On 11/15/2010 10:35 PM, Takuya Yoshikawa wrote:
>>>> In kvm_cpu_hotplug(), only CPU_STARTING case is protected by kvm_lock.
>>>> This patch adds missing protection for CPU_DYING case.
>>>>
>>>> Signed-off-by: Takuya Yoshikawa<yoshikawa.takuya@oss.ntt.co.jp>
>>>> ---
>>>> virt/kvm/kvm_main.c | 2 ++
>>>> 1 files changed, 2 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
>>>> index 339dd43..0fdd911 100644
>>>> --- a/virt/kvm/kvm_main.c
>>>> +++ b/virt/kvm/kvm_main.c
>>>> @@ -2148,7 +2148,9 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
>>>> case CPU_DYING:
>>>> printk(KERN_INFO "kvm: disabling virtualization on CPU%d\n",
>>>> cpu);
>>>> + spin_lock(&kvm_lock);
>>>> hardware_disable(NULL);
>>>> + spin_unlock(&kvm_lock);
>>>> break;
>>>> case CPU_STARTING:
>>>> printk(KERN_INFO "kvm: enabling virtualization on CPU%d\n",
>>>
>>> I believe this is correct.
>>
>> You mean lock is not necessary?
>
> 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?

   Takuya