------- Comment From [email protected] 2018-04-27 16:54 EDT------- I was told to write a small documentation describing what happens without the two patches mentioned in my comment #20.
We basically lose the ability to hotplug/unplug CPUs into virtual machines. Considering that blk-mq enqueue tasks using 'for_each_present_cpu()' (that iterates over CPUs in systems that don't support CPU hotplug - refer to those patches for technical details) we can also have problems if tasks are scheduled to CPUs present but not online. So I suggest to *not* run VMs with extra CPUs to be hotplugged later, like: -smp 8,sockets=1,cores=2,threads=8,maxcpus=16 or <vcpu placement='static' current='8'>16</vcpu> If we want a guest with 16 CPUs it's better to define it beforehand, for instance: -smp 16,sockets=1,cores=2,threads=8 or <vcpu placement='static'>16</vcpu> -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1759723 Title: ISST-LTE:KVM:Ubuntu18.04:BostonLC:boslcp3:boslcp3g3:Guest conosle hangs after hotplug CPU add operation. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu-power-systems/+bug/1759723/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
