On Mon, 2010-11-29 at 08:08 -1000, 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(); > } > > > 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? Can we identify precisely when it happens? If we can, we can try to force a hypervisor exit or re-register right after the data is copied over. This will force the per-cpu structure to get updated with good values. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html