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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 15/03/2019 18:35, John L. Poole wrote:
> 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.

You have a floating serial line, which is simulating you typing characters.

The '*' key is "run all diagnostic keyhandlers", and later it passes an
'R' which instructs Xen to reboot.

The keyhandlers start functioning as soon as we can possibly make them
after enabling interrupts, which is why you see it shortly after
setup_local_APIC()

~Andrew

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