From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v5] kvm: make vcpu life cycle separated from kvm instance Date: Mon, 26 Dec 2011 13:17:39 +0200 Message-ID: <4EF857D3.8020304@redhat.com> References: <1323657683-13934-1-git-send-email-kernelfans@gmail.com> <1324091975-20930-1-git-send-email-kernelfans@gmail.com> <20111226110943.GB2072@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Liu Ping Fan , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, aliguori@us.ibm.com, mtosatti@redhat.com, jan.kiszka@web.de To: Gleb Natapov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:51686 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753986Ab1LZLRo (ORCPT ); Mon, 26 Dec 2011 06:17:44 -0500 In-Reply-To: <20111226110943.GB2072@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 12/26/2011 01:09 PM, Gleb Natapov wrote: > > + > > + idx = srcu_read_lock(&kvm->srcu_vcpus); > > + kvm_for_each_vcpu(vcpu, kvm) { > > + if (!pass && !firststart && > > + vcpu != kvm->last_boosted_vcpu && > > + kvm->last_boosted_vcpu != NULL) { > > + vcpu = kvm->last_boosted_vcpu; > You access last_boosted_vcpu as if it is protected by srcu, but it > isn't. kvm_vcpu_release() changes it after synchronize_srcu_expedited() > call. > > I do not like this last_boosted_vcpu pointer much. May be we can rid of > it by remembering last apic_id and searching for it each time we enter > the function. I do not think this function is to performance sensitive. > We enter here when vcpu is spinning anyway. We aren't guaranteed to have an apic_id, so it has to be done using rcu, or maybe vcpu_id. I prefer using srcu, we can't run away from vcpu pointers. -- error compiling committee.c: too many arguments to function