@serge-hallyn: First step is to debug this issue and see if its a reasonable fix. If that's possible then we should leave qemu alone.
Second if we want to disable KSM for nested VMs relying on a 'QEMU' cpu isn't sufficient if someone uses a different -cpu flag. We could do: grep -q "Booting paravirtualized kernel on KVM" /var/log/kern.log && echo 0 > /sys/kernel/mm/ksm/run Or use tools like virt-what. Regardless I'll work on step 1. -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1413540 Title: qemu-kvm package enables KSM on VMs Status in linux package in Ubuntu: Incomplete Status in qemu package in Ubuntu: Confirmed Bug description: When installing qemu-kvm on a VM, KSM is enabled. I have encountered this problem in trusty:$ lsb_release -a Distributor ID: Ubuntu Description: Ubuntu 14.04.1 LTS Release: 14.04 Codename: trusty $ uname -a Linux juju-gema-machine-2 3.13.0-40-generic #69-Ubuntu SMP Thu Nov 13 17:53:56 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux The way to see the behaviour: 1) $ more /sys/kernel/mm/ksm/run 0 2) $ sudo apt-get install qemu-kvm 3) $ more /sys/kernel/mm/ksm/run 1 To see the soft lockups, deploy a cloud on a virtualised env like ctsstack, run tempest on it, the compute nodes of the virtualised deployment will eventually stop responding with (run tempest 2 times at least): 24096.072003] BUG: soft lockup - CPU#0 stuck for 23s! [qemu-system-x86:24791] [24124.072003] BUG: soft lockup - CPU#0 stuck for 23s! [qemu-system-x86:24791] [24152.072002] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791] [24180.072003] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791] [24208.072004] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791] [24236.072004] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791] [24264.072003] BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:24791] I am not sure whether the problem is that we are enabling KSM on a VM or the problem is that nested KSM is not behaving properly. Either way I can easily reproduce, please contact me if you need further details. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1413540/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
