From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762333AbYDCTmZ (ORCPT ); Thu, 3 Apr 2008 15:42:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761207AbYDCTd1 (ORCPT ); Thu, 3 Apr 2008 15:33:27 -0400 Received: from bzq-179-150-194.static.bezeqint.net ([212.179.150.194]:39113 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760707AbYDCTdA (ORCPT ); Thu, 3 Apr 2008 15:33:00 -0400 From: Avi Kivity To: kvm-devel@lists.sourceforge.net Cc: linux-kernel@vger.kernel.org, Glauber Costa Subject: [PATCH 26/35] x86: KVM guest: disable clock before rebooting. Date: Thu, 3 Apr 2008 22:32:41 +0300 Message-Id: <1207251170-5013-27-git-send-email-avi@qumranet.com> X-Mailer: git-send-email 1.5.4.5 In-Reply-To: <1207251170-5013-1-git-send-email-avi@qumranet.com> References: <1207251170-5013-1-git-send-email-avi@qumranet.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Glauber Costa This patch writes 0 (actually, what really matters is that the LSB is cleared) to the system time msr before shutting down the machine for kexec. Without it, we can have a random memory location being written when the guest comes back It overrides the functions shutdown, used in the path of kernel_kexec() (sys.c) and crash_shutdown, used in the path of crash_kexec() (kexec.c) Signed-off-by: Glauber Costa Signed-off-by: Avi Kivity --- arch/x86/kernel/kvmclock.c | 27 +++++++++++++++++++++++++++ 1 files changed, 27 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index b999f5e..ddee040 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -22,6 +22,7 @@ #include #include #include +#include #define KVM_SCALE 22 @@ -143,6 +144,28 @@ static void kvm_setup_secondary_clock(void) setup_secondary_APIC_clock(); } +/* + * After the clock is registered, the host will keep writing to the + * registered memory location. If the guest happens to shutdown, this memory + * won't be valid. In cases like kexec, in which you install a new kernel, this + * means a random memory location will be kept being written. So before any + * kind of shutdown from our side, we unregister the clock by writting anything + * that does not have the 'enable' bit set in the msr + */ +#ifdef CONFIG_KEXEC +static void kvm_crash_shutdown(struct pt_regs *regs) +{ + native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0); + native_machine_crash_shutdown(regs); +} +#endif + +static void kvm_shutdown(void) +{ + native_write_msr_safe(MSR_KVM_SYSTEM_TIME, 0, 0); + native_machine_shutdown(); +} + void __init kvmclock_init(void) { if (!kvm_para_available()) @@ -155,6 +178,10 @@ void __init kvmclock_init(void) pv_time_ops.set_wallclock = kvm_set_wallclock; pv_time_ops.sched_clock = kvm_clock_read; pv_apic_ops.setup_secondary_clock = kvm_setup_secondary_clock; + machine_ops.shutdown = kvm_shutdown; +#ifdef CONFIG_KEXEC + machine_ops.crash_shutdown = kvm_crash_shutdown; +#endif clocksource_register(&kvm_clock); } } -- 1.5.4.5