From mboxrd@z Thu Jan 1 00:00:00 1970 From: Randy Dunlap Subject: Re: linux-next: Tree for November 22 (kvm) Date: Mon, 29 Nov 2010 11:05:58 -0800 Message-ID: <4CF3F996.5070103@oracle.com> References: <20101122134911.b7e106f9.sfr@canb.auug.org.au> <20101122132627.bd4e88ef.randy.dunlap@oracle.com> <20101129083324.6870d7da.randy.dunlap@oracle.com> <4CF3D637.6060204@redhat.com> <4CF3E733.8090809@redhat.com> <4CF3E870.4040308@oracle.com> <4CF3EC1E.7050707@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4CF3EC1E.7050707@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Zachary Amsden Cc: Avi Kivity , Glauber Costa , Stephen Rothwell , kvm@vger.kernel.org, linux-next@vger.kernel.org, LKML List-Id: linux-next.vger.kernel.org On 11/29/10 10:08, Zachary Amsden wrote: > On 11/29/2010 07:52 AM, Randy Dunlap wrote: >> On 11/29/10 09:47, Zachary Amsden wrote: >> >>> On 11/29/2010 06:35 AM, Avi Kivity wrote: >>> >>>> On 11/29/2010 06:33 PM, Randy Dunlap wrote: >>>> >>>>> On Mon, 22 Nov 2010 13:26:27 -0800 Randy Dunlap wrote: >>>>> >>>>> >>>>>> On Mon, 22 Nov 2010 13:49:11 +1100 Stephen Rothwell wrote: >>>>>> >>>>>> >>>>>>> Hi all, >>>>>>> >>>>>>> Changes since 20101119: >>>>>>> >>>>>> >>>>>> kvm.c:(.init.text+0x11f49): undefined reference to >>>>>> >>>>> `kvm_register_clock' >>>>> >>>>>> when CONFIG_KVM_CLOCK is not enabled. >>>>>> >>>>> >>>>> BUild error still present in linux-next-2010-NOV-29. >>>>> >>>>> >>>> Glauber, Zach? >>>> >>>> >>> I can only speculate this reference is being called from smpboot without >>> CONFIG guarding? >>> >> Sorry, looks like I dropped the first line of the error messages: >> >> arch/x86/built-in.o: In function `kvm_smp_prepare_boot_cpu': >> kvm.c:(.init.text+0xad38): undefined reference to `kvm_register_clock' >> >> from arch/x86/kernel/kvm.c: >> >> #ifdef CONFIG_SMP >> static void __init kvm_smp_prepare_boot_cpu(void) >> { >> WARN_ON(kvm_register_clock("primary cpu clock")); >> kvm_guest_cpu_init(); >> native_smp_prepare_boot_cpu(); >> } >> >> so it looks like you are correct... >> > > Looks like this is the appropriate fix: > > #ifdef CONFIG_SMP > static void __init kvm_smp_prepare_boot_cpu(void) > { > #ifdef CONFIG_KVM_CLOCK > WARN_ON(kvm_register_clock("primary cpu clock")); > #endif > kvm_guest_cpu_init(); > native_smp_prepare_boot_cpu(); > } Sure, that works. Thanks. > > The SMP code is still buggy as well, wrt printk timing, in that it > doesn't get called early enough, correct? Has anyone thought of a good > solution to that problem? > > Basically the problem is CPU-1 will get CPU-0's per-cpu areas copied > over, and these are not valid for CPU-1. If the clocksource is used on > CPU-1 before kvm clock gets setup, it can go backwards, wreaking havoc, > causing panic, etc. > > What is the best test to guard against this? Perhaps we should keep the > CPU number in the per-cpu data and test against it? -- ~Randy *** Remember to use Documentation/SubmitChecklist when testing your code ***