Hi Peter,

There are some known hotplug issues on kernel-rt. For an example, see BZ1267425.

On this BZ I was able to identify the root cause by inspecting a
vmcore, and on these cases, the vmcore is the best tool to understand
why the system hanged.

Can you please capture a vmcore of the VM after it hangs on hotplug
operations?

Here is a document from support explaining how to capture a vmcore of a VM:

https://access.redhat.com/solutions/39604

We will also need the debuginfo packages of the kernel that was running
on the VM.

Peter, this issue has gone with rhel7.5. 


After online/offline 100 times using script in Description, both host and guest work well, not any error.

Versions:
3.10.0-730.rt56.658.el7.x86_64
qemu-kvm-rhev-2.10.0-1.el7.x86_64
libvirt-3.7.0-2.el7.x86_64
tuned-2.8.0-5.el7.noarch


Best Regards,
Pei

(In reply to Pei Zhang from comment #6)
> Peter, this issue has gone with rhel7.5. 
> 
> 
> After online/offline 100 times using script in Description, both host and
> guest work well, not any error.
> 
> Versions:
> 3.10.0-730.rt56.658.el7.x86_64
> qemu-kvm-rhev-2.10.0-1.el7.x86_64
> libvirt-3.7.0-2.el7.x86_64
> tuned-2.8.0-5.el7.noarch
> 
> 
> Best Regards,
> Pei

Thanks Pei!  Then I'm closing the bug.

Peter