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

[Zachary Amsden <zamsden@redhat.com>]

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?

Thanks,

Zach