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 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?