From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752941Ab3FJU2u (ORCPT ); Mon, 10 Jun 2013 16:28:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:12238 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751638Ab3FJU2t (ORCPT ); Mon, 10 Jun 2013 16:28:49 -0400 Date: Mon, 10 Jun 2013 17:19:33 -0300 From: Marcelo Tosatti To: Igor Mammedov Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, eabatalov89@gmail.com Subject: Re: [PATCH] x86: kvmclock: zero initialize pvclock shared memory area Message-ID: <20130610201933.GA31409@amt.cnet> References: <1370881871-13130-1-git-send-email-imammedo@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1370881871-13130-1-git-send-email-imammedo@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 10, 2013 at 06:31:11PM +0200, Igor Mammedov wrote: > === > Could be the following an acceptable fix? > === Read of kvmclock should return proper value from hypervisor: system timestamp + tsc delta. Should find the offender site and have it register MSR_KVM_SYSTEM_TIME before reading the area. > kernel might hung in pvclock_clocksource_read() due to > uninitialized memory might contain odd version value in > following cycle: > > do { > version = __pvclock_read_cycles(src, &ret, &flags); > } while ((src->version & 1) || version != src->version); > > if secondary kvmclock is accessed before it's registered with kvm. > > Clear garbage in pvclock shared memory area right after it's > allocated to avoid this issue. > > Ref: https://bugzilla.kernel.org/show_bug.cgi?id=59521 > Signed-off-by: Igor Mammedov > --- > arch/x86/kernel/kvmclock.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c > index d2c3812..3dd37eb 100644 > --- a/arch/x86/kernel/kvmclock.c > +++ b/arch/x86/kernel/kvmclock.c > @@ -242,6 +242,7 @@ void __init kvmclock_init(void) > if (!mem) > return; > hv_clock = __va(mem); > + memset(hv_clock, 0, size); > > if (kvm_register_clock("boot clock")) { > hv_clock = NULL; > -- > 1.7.1