kern/48277: Booting under KVM yields panic: siop_intr: I shouldn't be there !

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

>Number:         48277
>Category:       kern
>Synopsis:       Booting under KVM yields panic: siop_intr: I shouldn't be 
>there !
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Oct 05 15:50:00 +0000 2013
>Originator:     Andreas Gustafsson
>Release:        NetBSD 6.1.2 + patch (see below)
>Organization:
>Environment:
System: NetBSD 6.1.2
Architecture: x86_64
Machine: amd64
>Description:

I am attempting to install NetBSD on a virtual server hosted
by edis.at and based on the Linux KVM virtualization technology.
I am now trying NetBSD 6.1.2 plus a patch to force PCI configuration
mode 1 as in src/sys/arch/x86/pci/pci_machdep.c 1.61, to work around
PR 45671.

With this, I am able to boot the install media and install using
sysinst.  However, when booting the installed system, the kernel
panics (messages manually transcribed):

   acpicpu0 at cpu0: ACPI CPU
   panic: siop_intr: I shouldn't be there !
   fatal breakpoint trap in supervisor mode
   trap typ 1 code 0 rip ffffffff80252edd cs 8 rflags 246 cr2  0 cpl 6 rsp 
ffffffff80fc2c48
   Stopped in pid 0.1 (system) at  netbs:breakpoint+0x5:  leave
   db{0}>

>How-To-Repeat:

Order a KVM VPS from edis.at.  Ask them to configure a custom install
ISO with the download link
http://www.gson.org/netbsd/iso/NetBSD-6.1.2-pcimode1-amd64.iso .
Install.  Boot.

>Fix: