From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756820Ab3FSN3p (ORCPT ); Wed, 19 Jun 2013 09:29:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60096 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756481Ab3FSN3k (ORCPT ); Wed, 19 Jun 2013 09:29:40 -0400 Message-ID: <51C1B23B.7080703@redhat.com> Date: Wed, 19 Jun 2013 15:29:31 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 MIME-Version: 1.0 To: Batalov Eugene CC: Marcelo Tosatti , Eugene Batalov , kvm@vger.kernel.org, Igor Mammedov , linux-kernel@vger.kernel.org Subject: Re: [PATCHv1] kvm guest: fix uninitialized kvmclock read by KVM guest References: <20130610201933.GA31409@amt.cnet> <1371319305-590-1-git-send-email-ebatalov@parallels.com> <20130618222114.GC13856@amt.cnet> <51C1AC93.6010001@redhat.com> In-Reply-To: X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 19/06/2013 15:20, Batalov Eugene ha scritto: > > I've missed this detail. It looks like Igor's patch doesn't bring > secondary cpus kvm_clocksource behavior back to one before the regression, > Before the regression per_cpu variables are used to allocate > kvm_pv_clock areas. > To to usage of percpu variables bootstrap cpu kvm_clock area contents > were copied to smp secondary cpus kvm_clock areas when they were started. > Bootstrap cpu kvm_clock area was not zeroed at this time. > So kvm_pv_clock for secondary cpus never returned "zero" clock before > the regression. > > During the analysis of the bug I introduced idea to return zero before > kvm clocksource is initialized for secondary cpus > just like bootstrap cpu does on kernel boot. You can read that in BZ. Yes, this is why I prefer to invert the two function calls. But Igor's patch fixes the hang (trivially because version is even) and is more appropriate for -rc6. Paolo