Re: Xen BUG at page_alloc.c:1738 (Xen 4.5)

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 19/05/15 19:06, Major Hayden wrote:
> Hello there,
>
> I've been doing some testing of Xen 4.5 on Fedora 22 (due out within a week) and I have an error that prevents the server from booting in the very early boot process:
>
>> (XEN) Xen call trace:
>> (XEN)    [<ffff82d08011d160>] free_domheap_pages+0x240/0x430
>> (XEN)    [<ffff82d08018c944>] mmio_ro_do_page_fault+0x114/0x160
>> (XEN)    [<ffff82d0801a4c10>] do_page_fault+0x1a0/0x4f0
>> (XEN)    [<ffff82d080239768>] handle_exception_saved+0x2e/0x6c
>> (XEN) 
>> (XEN) 
>> (XEN) ****************************************
>> (XEN) Panic on CPU 0:
>> (XEN) Xen BUG at page_alloc.c:1738
>> (XEN) ****************************************
> The full output is over in a Github Gist[1].
>
> I've tested this on some physical machines (Dell, HP, and SuperMicro servers) as well as within a KVM virtual machine but I get the same boot error each time.  It occurs with Xen 4.5 and Linux 3.17-4.0.x.  Xen 4.5.1-rc1 fails in the same way.  I've opened a Red Hat Bug[2] as well as a Xen bug[3] on it.
>
> The code within free_domheap_pages() hasn't changed much since late 2014 so I'm not sure if that's the culprit.  Does anyone have any suggestions on how to debug it further?
>
> Thanks in advance!
>
> [1] https://gist.github.com/major/baa0e2eee7de51a2bcd1
> [2] https://bugzilla.redhat.com/show_bug.cgi?id=1219197
> [3] http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1908

Can you try a debug hypervisor and rerun, to confirm the stack trace and
see whether any assertions fire.

Can you identify exactly which line xen/common/page_alloc.c:1738 is in
your source?

~Andrew