From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758178AbbBEQol (ORCPT ); Thu, 5 Feb 2015 11:44:41 -0500 Received: from e06smtp15.uk.ibm.com ([195.75.94.111]:38952 "EHLO e06smtp15.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753953AbbBEQoj (ORCPT ); Thu, 5 Feb 2015 11:44:39 -0500 Message-ID: <54D39DF0.3020109@de.ibm.com> Date: Thu, 05 Feb 2015 17:44:32 +0100 From: Christian Borntraeger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: riel@redhat.com, kvm@vger.kernel.org CC: linux-kernel@vger.kernel.org, mtosatti@redhat.com, mingo@kernel.org, ak@linux.intel.com, oleg@redhat.com, masami.hiramatsu.pt@hitachi.com, fweisbec@gmail.com, paulmck@linux.vnet.ibm.com, lcapitulino@redhat.com, pbonzini@redhat.com Subject: Re: [PATCH 4/4] kvm,rcu: use RCU extended quiescent state when running KVM guest References: <1423154134-17391-1-git-send-email-riel@redhat.com> <1423154134-17391-5-git-send-email-riel@redhat.com> In-Reply-To: <1423154134-17391-5-git-send-email-riel@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15020516-0021-0000-0000-000002CE7584 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 05.02.2015 um 17:35 schrieb riel@redhat.com: > From: Rik van Riel > > The host kernel is not doing anything while the CPU is executing > a KVM guest VCPU, so it can be marked as being in an extended > quiescent state, identical to that used when running user space > code. > > The only exception to that rule is when the host handles an > interrupt, which is already handled by the irq code, which > calls rcu_irq_enter and rcu_irq_exit. > > The guest_enter and guest_exit functions already switch vtime > accounting independent of context tracking, so leave those calls > where they are, instead of moving them into the context tracking > code. > > Signed-off-by: Rik van Riel > --- > include/linux/context_tracking.h | 8 +++++++- > include/linux/context_tracking_state.h | 1 + > 2 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h > index bd9f000fc98d..a5d3bb44b897 100644 > --- a/include/linux/context_tracking.h > +++ b/include/linux/context_tracking.h > @@ -43,7 +43,7 @@ static inline enum ctx_state exception_enter(void) > static inline void exception_exit(enum ctx_state prev_ctx) > { > if (context_tracking_is_enabled()) { > - if (prev_ctx == IN_USER) > + if (prev_ctx == IN_USER || prev_ctx == IN_GUEST) > context_tracking_user_enter(prev_ctx); > } > } > @@ -78,6 +78,9 @@ static inline void guest_enter(void) > vtime_guest_enter(current); > else > current->flags |= PF_VCPU; > + > + if (context_tracking_is_enabled()) > + context_tracking_user_enter(IN_GUEST); > } Couldnt we make rcu_virt_note_context_switch(smp_processor_id()); conditional in include/linux/kvm_host.h (kvm_guest_enter) e.g. something like if (!context_tracking_is_enabled()) rcu_virt_note_context_switch(smp_processor_id());