port-xen/49721: Running ATF tests crashes NetBSD 5 Xen domU

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         49721
>Category:       port-xen
>Synopsis:       Running ATF tests crashes NetBSD 5 Xen domU
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-xen-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Mar 05 15:30:00 +0000 2015
>Originator:     Andreas Gustafsson
>Release:        NetBSD 5.2.3
>Organization:
>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

In a comment to PR 47157, I said:

   Issue 5: After manually starting xencommons and xend (in that order),
   I tried installing a NetBSD 5.2 domU and running the ATF tests using

      anita --vmm xen test http://ftp.netbsd.org/pub/NetBSD/NetBSD-5.2/amd64/

    This ended in a domU kernel panic while running the fs/tmpfs/t_rename
    test.  This is reproducible, and also happens with a 5.1 domU, though
    the exact test where the panic happens varies; so far, it has happened
    in fs/tmpfs/t_rename, fs/tmpfs/t_remove, and fs/tmpfs/t_link.  A 6.0.1
    domU is not affected by this.

Since PR 47157 was focused on documentation issues and has now been closed,
I am opening a separate PR to track the NetBSD 5 panic issue.

>How-To-Repeat:

Running the following shell script will reproduce the bug by doing an
automated install of NetBSD/amd64 6.1.5 with Xen 4.2 in a qemu virtual
machine, installing a NetBSD 5.2.3 domU, and running the ATF tests in 
it.

    http://www.gson.org/netbsd/bugs/xen/crash-xen-domu.sh

Anita version 1.37 (in pkgsrc-current as misc/py-anita) is recommended
since some earlier versions can't reliably run a recursive invocation
of anita in the VM.  You also need about 5 GB of disk space.

Before blaming qemu, please note that qemu was not involved in the
original panics reported in PR 47157.

>Fix: