From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takuya Yoshikawa Subject: Re: [PATCH 1/2] KVM: take kvm_lock for hardware_disable() during cpu hotplug Date: Thu, 18 Nov 2010 11:04:22 +0900 Message-ID: <4CE489A6.4010100@oss.ntt.co.jp> References: <20101116173244.c5d2e812.yoshikawa.takuya@oss.ntt.co.jp> <20101116173502.96ff13f3.yoshikawa.takuya@oss.ntt.co.jp> <4CE4889A.7010808@redhat.com> 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: Zachary Amsden Return-path: Received: from serv2.oss.ntt.co.jp ([222.151.198.100]:48001 "EHLO serv2.oss.ntt.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753976Ab0KRCCS (ORCPT ); Wed, 17 Nov 2010 21:02:18 -0500 In-Reply-To: <4CE4889A.7010808@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: (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?