Does this fix need to be applied to 3.16 as well? Or is backporting to Vivid/3.19 sufficient?
** Description changed: + [Impact] + Stop/continue via qemu monitor can easily trigger soft-lockups due to incorrect VM timekeeping. + + [Test Case] + On a single CPU KVM guest: + yes > /dev/null & + + Followed by + (qemu) stop + + Wait a while, then: + (qemu) cont + + [Fix] + The following commits upstream: + commit 545a2bf742fb41f17d03486dd8a8c74ad511dec2 + commit 4be1b29795d692d512bb67b770665d6f8ea5cb0b + + -- + == Comment: #0 - Cyril Bur <[email protected]> - 2015-02-23 18:03:41 == +++ This bug was initially created as a clone of Bug #108455 +++ I was investigating the cause of some ppc64le KVM guest softlockup warnings. On a single CPU KVM guest, I ran something to keep the guest busy: yes > /dev/null & Followed by (qemu) stop Wait a while, then: (qemu) cont We get a softlockup error: BUG: soft lockup - CPU#0 stuck for 9220s! [yes:2389] .__getnstimeofday .getnstimeofday .ktime_get_real .netif_receive_skb .ibmveth_poll .net_rx_action .__do_softirq .irq_exit .__do_irq .call_do_irq .do_IRQ I was going to file it away in the "don't do that" bin, but I notice x86 have something to detect a paused VM and avoid spewing the soft lockup error. Do we need something like this on ppc64? commit 5d1c0f4a80a6df73395fb3fc2c302510f8f09d36 Author: Eric B Munson <[email protected]> Date: Sat Mar 10 14:37:28 2012 -0500 - watchdog: add check for suspended vm in softlockup detector + watchdog: add check for suspended vm in softlockup detector - A suspended VM can cause spurious soft lockup warnings. To avoid these, the - watchdog now checks if the kernel knows it was stopped by the host and skips - the warning if so. When the watchdog is reset successfully, clear the guest - paused flag. + A suspended VM can cause spurious soft lockup warnings. To avoid these, the + watchdog now checks if the kernel knows it was stopped by the host and skips + the warning if so. When the watchdog is reset successfully, clear the guest + paused flag. == Comment: #1 - Cyril Bur <[email protected]> - 2015-02-23 18:03:55 == Hi, I have been working on a fix for guest kernels. This requires two patches: 1/2 commit 545a2bf742fb41f17d03486dd8a8c74ad511dec2 Author: Cyril Bur <[email protected]> Date: Thu Feb 12 15:01:24 2015 -0800 - kernel/sched/clock.c: add another clock for use with the soft lockup + kernel/sched/clock.c: add another clock for use with the soft lockup watchdog - and 2/2 commit 4be1b29795d692d512bb67b770665d6f8ea5cb0b Author: Cyril Bur <[email protected]> Date: Thu Feb 12 15:01:28 2015 -0800 - powerpc: add running_clock for powerpc to prevent spurious + powerpc: add running_clock for powerpc to prevent spurious softlockup warnings Both are in upstream. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1427075 Title: Stopping and starting KVM partitions results in guest kernel softlockup To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1427075/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
