[Libguestfs] Libguestfs Hangs on CentOS 7.4

[Richard W.M. Jones]

On Mon, Dec 11, 2017 at 02:28:31PM +0000, Phill Bandelow wrote:
> Hi,
> 
> We seem to be hitting an issue where libguestfs keeps hanging. virt-resize,
> guestmount etc.. never complete. If we set
> LIBGUESTFS_BACKEND_SETTINGS=force_tcg it completes.
> 
> The issue starts when updating to CentOS 7.4 (CentOS 7.3 work fine). It
> doesn't seem to affect all 7.4 hypervisors and the only similarity that we
> have found is that they all use NVMe drives.

I've seen this issue before where the UART hangs, and I can't put my
finger on what was causing it right now.

At any rate there's a few things you can look into:

(1) Try with LIBGUESTFS_BACKEND=direct (without forcing TCG).

(2) Is it using nested KVM?  Is nested KVM enabled in the KVM
module in the host kernel:

  # systool -m kvm_intel -v | grep nested

(should say "Y" if yes)

If nested KVM is enabled, you can disable it (probably requires a
reboot unfortunately).  Or if disabled, try enabling it.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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