Hi Expert:
The VM is hung here after (2, or 3, or 5 and the longest time is 10 hours) by qemu-kvm.
Notes:
for VM:
OS: RHEL8.1
CPU: 1
MEM:4G
For qemu-kvm(host kernel RHEL7):
1) version:
/usr/libexec/qemu-kvm -version
QEMU emulator version 2.10.0(qemu-kvm-ev-2.10.0-21.el7_5.4.1)
2) once the issue is occurred, the CPU of "CPU0 /KVM" is more than 99% by com "top -p VM_pro_ID"
PID UDER PR NI RES S % CPU %MEM TIME+ COMMAND
872067 qemu 20 0 1.6g R 99.9 0.6 37:08.87 CPU 0/KVM
3) use "pstack 493307" and below is function trace
Thread 1 (Thread 0x7f2572e73040 (LWP 872067)):
#0 0x00007f256cad8fcf in ppoll () from /lib64/libc.so.6
#1 0x000055ff34bdf4a9 in qemu_poll_ns ()
#2 0x000055ff34be02a8 in main_loop_wait ()
#3 0x000055ff348bfb1a in main ()
4) use strace "strace -tt -ff -p 872067 -o cfx" and below log keep printing
21:24:02.977833 ppoll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=8, events=POLLIN}, {fd=9, events=POLLIN}, {fd=80, events=POLLIN}, {fd=82, events=POLLIN}, {fd=84, events=POLLIN}, {fd=115, events=POLLIN}, {fd=121, events=POLLIN}], 9, {0, 0}, NULL, 8) = 0 (Timeout)
21:24:02.977918 ppoll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=8, events=POLLIN}, {fd=9, events=POLLIN}, {fd=80, events=POLLIN}, {fd=82, events=POLLIN}, {fd=84, events=POLLIN}, {fd=115, events=POLLIN}, {fd=121, events=POLLIN}], 9, {0, 911447}, NULL, 8) = 0 (Timeout)
21:24:02.978945 ppoll([{fd=4, events=POLLIN}, {fd=6, events=POLLIN}, {fd=8, events=POLLIN}, {fd=9, events=POLLIN}, {fd=80, events=POLLIN}, {fd=82, events=POLLIN}, {fd=84, events=POLLIN}, {fd=115, events=POLLIN}, {fd=121, events=POLLIN}], 9, {0, 0}, NULL, 8) = 0 (Timeout)
Therefore, I think the thread "CPU 0/KVM" is in tight loop.
5) use reset can recover this issue. however, it will reoccurred again.
Current work around is increase one CPU for this VM, then issue is gone.
thanks
Cliff
one changes:
Guest VM is Red Hat Enterprise Linux 8.1 (Ootpa).
there is no issue once guest VM is RHEL7.6.