From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: [PATCH 2/2] KVM: make guest mode entry to be rcu quiescent state Date: Wed, 4 May 2011 16:31:04 +0300 Message-ID: <1304515864-17105-3-git-send-email-gleb@redhat.com> References: <1304515864-17105-1-git-send-email-gleb@redhat.com> Cc: avi@redhat.com, mtosatti@redhat.com, kvm@vger.kernel.org, paulmck@linux.vnet.ibm.com To: linux-kernel@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:25778 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753561Ab1EDNbQ (ORCPT ); Wed, 4 May 2011 09:31:16 -0400 In-Reply-To: <1304515864-17105-1-git-send-email-gleb@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: KVM does not hold any references to rcu protected data when it switches CPU into a guest mode. In fact switching to a guest mode is very similar to exiting to userspase from rcu point of view. In addition CPU may stay in a guest mode for quite a long time (up to one time slice). Lets treat guest mode as quiescent state, just like we do with user-mode execution. Signed-off-by: Gleb Natapov --- include/linux/kvm_host.h | 9 +++++++++ 1 files changed, 9 insertions(+), 0 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 0bc3d37..244413f 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -591,8 +591,17 @@ static inline int kvm_deassign_device(struct kvm *kvm, static inline void kvm_guest_enter(void) { + BUG_ON(preemptible()); account_system_vtime(current); current->flags |= PF_VCPU; + /* KVM does not hold any references to rcu protected data when it + * switches CPU into a guest mode. In fact switching to a guest mode + * is very similar to exiting to userspase from rcu point of view. In + * addition CPU may stay in a guest mode for quite a long time (up to + * one time slice). Lets treat guest mode as quiescent state, just like + * we do with user-mode execution. + */ + rcu_virt_note_context_switch(smp_processor_id()); } static inline void kvm_guest_exit(void) -- 1.7.4.4