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Description of problem:
Guest hangs after save, restore guest with 280 vcpus
Version-Release number of selected component (if applicable):
libvirt-3.2.0-14.el7_4.3.x86_64
qemu-kvm-rhev-2.9.0-16.el7_4.5.x86_64
kernel: 3.10.0-693.2.1.el7.x86_64
rhel7.4 Guest kernel: 3.10.0-693.el7.x86_64
How reproducible:
100%
Steps to Reproduce:
1. Start guest with 280 vcpus with xml below:
<vcpu placement='static'>280</vcpu>
......
<os>
<type arch='x86_64' machine='pc-q35-rhel7.4.0'>hvm</type>
</os>
......
<cpu mode='host-model'>
<model fallback='allow'/>
</cpu>
......
<iommu model='intel'>
<driver intremap='on' eim='on'/>
</iommu>
</devices>
......
2. Login to the guest, check there are 280 vcpus
# cat /proc/cpuinfo |grep processor|wc -l
280
3. Save and restore the guest
# virsh save r7-4t r7-4t.save
Domain r7-4t saved to r7-4t.save
# virsh restore r7-4t.save
Domain restored from r7-4t.save
4. Try to login to the guest, the virsh console hang.
# virsh console r7-4t
Connected to domain r7-4t
Escape character is ^]
[ 367.342608] INFO: task xfsaild/dm-0:2076 blocked for more than 120 seconds.
[ 367.343583] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
1) Sometimes, we can get these error messages in console when save, restore guest with 261 cpus:
[ 69.647147] NMI watchdog: BUG: soft lockup - CPU#9 stuck for 22s! [kworker/u538:5:1944]
[ 97.647211] NMI watchdog: BUG: soft lockup - CPU#9 stuck for 22s! [kworker/u538:5:1944]
[ 104.278141] INFO: rcu_sched self-detected stall on CPU[ 104.280038] INFO: rcu_sched detected stalls on CPUs/tasks:
2) Try to login guest through virt-manager, can't input the login user.
5. Change the vcpu to 248, then redo step1-4.
In Step4, login to guest successfully, and check there are 248 cpus.
Actual result:
In step4, save restore guest with 280 cpus, failed to login to guest, or the operations in guest hang(260<vcpu<263).
Expected result:
In step4, save restore guest with cpu<=384, can login to guest and do operations successfully.
Comment 2Martin Kletzander
2017-10-10 12:17:11 UTC
This seems like another underlying issue is causing this, so I'm moving this to QEMU for further triage.
Description of problem: Guest hangs after save, restore guest with 280 vcpus Version-Release number of selected component (if applicable): libvirt-3.2.0-14.el7_4.3.x86_64 qemu-kvm-rhev-2.9.0-16.el7_4.5.x86_64 kernel: 3.10.0-693.2.1.el7.x86_64 rhel7.4 Guest kernel: 3.10.0-693.el7.x86_64 How reproducible: 100% Steps to Reproduce: 1. Start guest with 280 vcpus with xml below: <vcpu placement='static'>280</vcpu> ...... <os> <type arch='x86_64' machine='pc-q35-rhel7.4.0'>hvm</type> </os> ...... <cpu mode='host-model'> <model fallback='allow'/> </cpu> ...... <iommu model='intel'> <driver intremap='on' eim='on'/> </iommu> </devices> ...... 2. Login to the guest, check there are 280 vcpus # cat /proc/cpuinfo |grep processor|wc -l 280 3. Save and restore the guest # virsh save r7-4t r7-4t.save Domain r7-4t saved to r7-4t.save # virsh restore r7-4t.save Domain restored from r7-4t.save 4. Try to login to the guest, the virsh console hang. # virsh console r7-4t Connected to domain r7-4t Escape character is ^] [ 367.342608] INFO: task xfsaild/dm-0:2076 blocked for more than 120 seconds. [ 367.343583] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. 1) Sometimes, we can get these error messages in console when save, restore guest with 261 cpus: [ 69.647147] NMI watchdog: BUG: soft lockup - CPU#9 stuck for 22s! [kworker/u538:5:1944] [ 97.647211] NMI watchdog: BUG: soft lockup - CPU#9 stuck for 22s! [kworker/u538:5:1944] [ 104.278141] INFO: rcu_sched self-detected stall on CPU[ 104.280038] INFO: rcu_sched detected stalls on CPUs/tasks: 2) Try to login guest through virt-manager, can't input the login user. 5. Change the vcpu to 248, then redo step1-4. In Step4, login to guest successfully, and check there are 248 cpus. Actual result: In step4, save restore guest with 280 cpus, failed to login to guest, or the operations in guest hang(260<vcpu<263). Expected result: In step4, save restore guest with cpu<=384, can login to guest and do operations successfully.