[Xen-devel] [BUG] Sporadic boot of Xen Kernel 4.12.0, hangs at random EXTInt

["John L. Poole" <jlpoole56@xxxxxxxxx>]

I have a Supermicro Intel Atom based server with UEFI.  I purchased the
server in November 2016 intending to run Xen server.  I was able
to overcome some problem in 2016 with help from the Xen Project and
I was able to load a xen kernel built in Gentoo for Gentoo VMs manually
using the EFI command.  At that time, I was told grub2 was not UEFI ready.

Now I have been trying to integrate grub2 with Xen using kernel version
4.19.23-gentoo.  I am witnessing boot attempts that fail at different
points just after calls to setup_local_APIC in apic.c. Sometimes I am
successful in loading the Xen Kernel and then everything goes smoothly
loading the DOM0 session.  I can then load the VMs and everything
seems okay.  But most of the time, the boot up hangs in
between calls to the function setup_local_APIC in apic.c.

I had posted to the XEN Users list and had little, if any, response.
I have created two bugs within Gentoo's system, differentiated by
xen kernels:

4.11.1       at  https://bugs.gentoo.org/679826
4.12.0_rc4   at  https://bugs.gentoo.org/680472

What is really vexing is the randomness of results.  For instance, here
a log from this morning of success vs. failures:

9:17 AM 3/15/2019   2   (XEN) [2019-03-15 16:17:33] Adding cpu 2 to 
runqueue 0
9:18 AM 3/15/2019   5   (XEN) [2019-03-15 16:18:53] Adding cpu 5 to 
runqueue 0
9:19 AM 3/15/2019   SUCCESS!!
after * key in serial port for "diagnostics all", shutdown by watchdog.
9:30 AM 3/15/2019   SUCCESS!!
(XEN) [2019-03-15 16:32:54] Hardware Dom0 shutdown: watchdog rebooting 
machine
9:34 AM 3/15/2019   Before 1: (XEN) [2019-03-15 16:34:14] HVM: HAP page 
sizes: 4kB, 2MB
9:35 AM 3/15/2019   3
9:36 AM 3/15/2019   4   (XEN) [2019-03-15 16:37:21] Adding cpu 4 to 
runqueue 0
9:37 AM 3/15/2019   Before 1: (XEN) [2019-03-15 16:38:33] HVM: HAP page 
sizes: 4kB, 2MB
9:39 AM 3/15/2019   SUCCESS!!

My attempt to isolate the failure point has been unsuccessful. I'm prepared
to patch 4.12.0_rc4 if that will help, my previous attempt in 4.11.1 only
allowed me to conclude that the problem is not within apic.c.

John Poole

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