From mboxrd@z Thu Jan  1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 59521] KVM linux guest reads uninitialized pvclock values
 before executing rdmsr MSR_KVM_WALL_CLOCK
Date: Tue, 11 Jun 2013 16:03:56 +0000 (UTC)
Message-ID: <20130611160356.3883011FB35@bugzilla.kernel.org>
References: <bug-59521-28872@https.bugzilla.kernel.org/>
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
To: kvm@vger.kernel.org
Return-path: <kvm-owner@vger.kernel.org>
Received: from mail.kernel.org ([198.145.19.201]:50019 "EHLO mail.kernel.org"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1752485Ab3FKQD7 (ORCPT <rfc822;kvm@vger.kernel.org>);
	Tue, 11 Jun 2013 12:03:59 -0400
Received: from mail.kernel.org (localhost [127.0.0.1])
	by mail.kernel.org (Postfix) with ESMTP id EC6B420391
	for <kvm@vger.kernel.org>; Tue, 11 Jun 2013 16:03:57 +0000 (UTC)
Received: from bugzilla.kernel.org (bugzilla.kernel.org [198.145.19.217])
	by mail.kernel.org (Postfix) with ESMTP id 5EA882038B
	for <kvm@vger.kernel.org>; Tue, 11 Jun 2013 16:03:56 +0000 (UTC)
In-Reply-To: <bug-59521-28872@https.bugzilla.kernel.org/>
Sender: kvm-owner@vger.kernel.org
List-ID: <kvm.vger.kernel.org>

https://bugzilla.kernel.org/show_bug.cgi?id=59521





--- Comment #1 from Eugene Batalov <eabatalov89@gmail.com>  2013-06-11 16:03:55 ---
I have reconstructed the uninitialized pvclock read backtrace.
References to file lines are for Ubuntu-raring kernel
git://kernel.ubuntu.com/ubuntu/ubuntu-raring.git
tag is Ubuntu-3.8.0-19.30

bp: 0xf3ccbe68 ip: 0xc103cfbd
arch/x86/include/asm/pvclock.h:78
arch/x86/kernel/pvclock.c:74
bp: 0xf3ccbe70 ip: 0xc103c057
arch/x86/kernel/kvmclock.c:91
bp: 0xf3ccbe78 ip: 0xc1017598
arch/x86/kernel/tsc.c:58
bp: 0xf3ccbea8 ip: 0xc107e98d
kernel/sched/clock.c:248
bp: 0xf3ccbeb8 ip: 0xc107ea35
kernel/sched/clock.c:342
bp: 0xf3ccbf08 ip: 0xc104ad85
kernel/printk.c:356
bp: 0xf3ccbf50 ip: 0xc104c4e1
kernel/printk.c:1607
bp: 0xf3ccbf70 ip: 0xc1609bb6
kernel/printk.c:1688
bp: 0xf3ccbf90 ip: 0xc1600a51
arch/x86/include/asm/bitops.h:321
arch/x86/kernel/cpu/common.c:1325
bp: 0xf3ccbfb4 ip: 0xc1604000
??
bp: 0x00000000


kernel/printk.c:356
calls local_clock()
calls sched_clock_cpu()
calls sched_clock()
calls paravirt_sched_clock()
calls indirectly kvm_clock_read()
unintialized pv_clock is read here

vcpu kvmclock initialization is performed in kvm_register_clock.
kvm_register_clock is called from
static void __init kvm_smp_prepare_boot_cpu(void)
called form
 ./init/main.c:524 as smp_prepare_boot_cpu

I'll think about proper fix soon. We probably should fix cpu initialization
stages order or disable usage of pvclock before it initialized.

-- 
Configure bugmail: https://bugzilla.kernel.org/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are watching the assignee of the bug.