From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zachary Amsden Subject: Re: [PATCH 1/2] KVM: take kvm_lock for hardware_disable() during cpu hotplug Date: Wed, 17 Nov 2010 16:33:51 -1000 Message-ID: <4CE4908F.3050209@redhat.com> References: <20101116173244.c5d2e812.yoshikawa.takuya@oss.ntt.co.jp> <20101116173502.96ff13f3.yoshikawa.takuya@oss.ntt.co.jp> <4CE4889A.7010808@redhat.com> <4CE489A6.4010100@oss.ntt.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: avi@redhat.com, mtosatti@redhat.com, kvm@vger.kernel.org, takuya.yoshikawa@gmail.com To: Takuya Yoshikawa Return-path: Received: from mx1.redhat.com ([209.132.183.28]:17249 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754848Ab0KRCd5 (ORCPT ); Wed, 17 Nov 2010 21:33:57 -0500 In-Reply-To: <4CE489A6.4010100@oss.ntt.co.jp> Sender: kvm-owner@vger.kernel.org List-ID: 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 >>> --- >>> 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