From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: Re: [PATCH] disable clock before rebooting. Date: Fri, 07 Mar 2008 11:23:34 -0300 Message-ID: <47D14FE6.1000300@redhat.com> References: <1204820092-16532-1-git-send-email-gcosta@redhat.com> <47D107CE.1040601@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel@lists.sourceforge.net To: Avi Kivity Return-path: In-Reply-To: <47D107CE.1040601@qumranet.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces@lists.sourceforge.net Errors-To: kvm-devel-bounces@lists.sourceforge.net List-Id: kvm.vger.kernel.org Avi Kivity wrote: > Glauber Costa wrote: >> This patch writes 0 (actually, what really matters is that the >> LSB is cleared) to the system time msr before rebooting/shutting down >> the machine. >> >> Without it, we can have a random memory location being written >> when the guest comes back >> if (!kvm_para_available()) >> @@ -154,6 +181,11 @@ 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.emergency_restart = kvm_emergency_restart; >> + machine_ops.shutdown = kvm_shutdown; >> + machine_ops.restart = kvm_restart; >> + machine_ops.halt = kvm_halt; >> + machine_ops.power_off = kvm_power_off; >> clocksource_register(&kvm_clock); >> } >> } >> > > Oh, I think that these are all unnecessary. You need to stop the clock > only if the memory it uses will be reused. Halt, shutdown and poweroff > clearly don't. Resets need to go through the host anyway, since they > can be invoked without the guest knowing about it. power off, agreed. halt, it doesn't really do anything anyway in reboot.c, and is here just for "future completeness". > The only case I can think of where we need to stop the clock is kexec. > as for kexec, it uses precisely the shutdown function, doesn't it? Or is it crash_shutdown? Humm, /me looks, and I think it's the later, right? If this is true and resets goes through the host, then we don't even need the header exports. Ingo'll be happy. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/