[Xen-devel] 4.9.19 (and others) hang when running as a nested dom0

[George Dunlap <george.dunlap@xxxxxxxxxx>]

I normally test CentOS using nested virtualization (mainly because
it's easy to restore the disk to a known state).  At some point in the
last six months this basically stopped working, as newer kernels (and
even backports) stopped booting properly under Xen.

I've finally gotten around to building my own kernel outside of the
normal RPM / CentOS build system to reproduce the issue.

I downloaded the 4.9.19 tarball and compiled under CentOS 6 with the
attached config.

The console output for the VM when running as a simple domU is
attached as native-vm.console.

Then console output when running with Xen inside the VM and the Linux
kernel as a dom0 inside that guest is attached as L1-dom0.console.
(That is, the dom0 for L1, as opposed to the dom0 for L0.  Not clear
how the terminology should apply here.)

As you can see, native-vm boots to completion, whereas L1 hangs just
after deciding to use clocksource as the TSC.

The guest appears to be mostly but not completely idle -- as one would
expect if dom0 just decided it didn't have anything to do.

Any ideas on how to proceed?

 -George

Attachment: xl-dmesg.txt
Description: Text document

Attachment: config-4.9.19
Description: Binary data

Attachment: L1-dom0.console
Description: Binary data

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