Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030424Ab3FUJCv (ORCPT ); Fri, 21 Jun 2013 05:02:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:9228 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965400Ab3FUJCs (ORCPT ); Fri, 21 Jun 2013 05:02:48 -0400 From: Igor Mammedov To: linux-kernel@vger.kernel.org Cc: mtosatti@redhat.com, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, kvm@vger.kernel.org, x86@kernel.org, pbonzini@redhat.com, eabatalov89@gmail.com Subject: [PATCH 1/2] x86: kvmclock: zero initialize pvclock shared memory area Date: Fri, 21 Jun 2013 11:01:20 +0200 Message-Id: <1371805281-21305-2-git-send-email-imammedo@redhat.com> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1526 Lines: 47 Since commit: 7069ed6 x86: kvmclock: allocate pvclock shared memory 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. Additionally before regression was introduced users of pre-cpu hv_clock were relying on variable being zero initialized, and 7069ed6 breaks this assumption for usage of: hv_clock.migrate_count which could be populated with random garbage now. Clearing garbage in pvclock shared memory area right after it's allocated helps to avoid these issues. 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/