port-i386/53064: i386 kernel fault under VirtualBox

[bch <brad.harder%gmail.com@localhost>]

>Number:         53064
>Category:       port-i386
>Synopsis:       fault on boot in Oracle VirtualBox VM
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-i386-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Mar 02 01:30:00 +0000 2018
>Originator:     bch <brad.harder%gmail.com@localhost>
>Release:        NetBSD 8.99.12
>Organization:
method logic digital
>Environment:
System: NetBSD daily build from nycdn.netbsd.org, i386
Architecture: i386
Machine: i386 Virtual
>Description:
Kernel fault booting under VirtualBox
Transcribed by hand:

...
attimer0: attached to pcppi0
uvm_fault(0xc136b640, 0, 1) -> 0xe
fatal page fault in supervisor mode
trap type 6 code 0 eip 0xc0100e08 cs 0x8 eflags 0x10082 c42 0x5 ilevel
0x8 esp 0 x1
curlwp 0xc3a18540 pid 0 lid 17 lowest kstack 0xdaecc2c0
kernel: supervisor trap page fault, code=0
Stopped in pid 0.17 (system) at netbsd:Xspllower+0x18: addb %ah,5(%ebx)
>How-To-Repeat:
 I seemed to get this fault w/ 6.x, 7.x, and -current (i386) all the
same. This was under latest VirtualBox from Oracle on Win 7.
>Fix: