>Number:         34209
>Category:       port-xen
>Synopsis:       Login to a DomU's xdm crashes the DomU
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    port-xen-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Aug 16 01:30:00 +0000 2006
>Originator:     Mark Weinem
>Release:        Dom0: NetBSD 4_Beta, DomU: NetBSD 3-stable
>Organization:
>Environment:
Dom0 is a setup from: NetBSD-daily/netbsd-4/200608150000Z/i386/

DomU is a setup from: NetBSD-daily/netbsd-3/200608120000Z/i386/
>Description:
# panic: HYPERVISOR_mmu_update failed

Stopped in pid 427.1 (XFree86) at       
netbsd:cpu_Debugger+0x4:        popl    %ebp
cpu_Debugger(c03fdefe,cb81bcd8,cb81bcec,c0383f4f,ca3e95f0) at netbsd:cpu_Debugger+0x4
panic(c03feabe,0,cb81bd6c,0,38890b90) at netbsd:panic+0x135
xpq_flush_queue(38890b90,f8025,ffffffff,0,bdbff000) at netbsd:xpq_flush_queue+0x5c
pmap_enter(ca3e95f0,bdae4000,f8000,1,21) at netbsd:pmap_enter+0x71e
udv_fault(cb81bec4,bdae4000,cb81be44,1,0) at netbsd:udv_fault+0x12b
uvm_fault(cb8241c4,bdae4000,0,1,44e27fb2) at netbsd:uvm_fault+0x1080
trap() at netbsd:trap+0x304
--- trap (number 6) ---
0xbdb8607d:
ds          0x11
es          0x11
fs          0x31
gs          0x11
edi         0xc03feabe  copyright+0x110de
esi         0x100
ebp         0xcb81bc9c
ebx         0xcb81bcd8
edx         0xc0532000  emul_freebsd_object+0xb2fe0
ecx         0xfffffc00
eax         0x1
eip         0xc037b9a4  cpu_Debugger+0x4
cs          0x9
eflags      0x202
esp         0xcb81bc9c
ss          0x11
netbsd:cpu_Debugger+0x4:        popl    %ebp
Stopped in pid 427.1 (XFree86) at       
netbsd:cpu_Debugger+0x4:        popl    %ebp
---

db> trace
cpu_Debugger(c03fdefe,cb81bcd8,cb81bcec,c0383f4f,ca3e95f0) 
at netbsd:cpu_Debugger+0x4
panic(c03feabe,0,cb81bd6c,0,38890b90) at netbsd:panic+0x135
xpq_flush_queue(38890b90,f8025,ffffffff,0,bdbff000) at netbsd:xpq_flush_queue+0x5c
pmap_enter(ca3e95f0,bdae4000,f8000,1,21) at netbsd:pmap_enter+0x71e
udv_fault(cb81bec4,bdae4000,cb81be44,1,0) at netbsd:udv_fault+0x12b
uvm_fault(cb8241c4,bdae4000,0,1,44e27fb2) at netbsd:uvm_fault+0x1080
trap() at netbsd:trap+0x304
--- trap (number 6) ---
0xbdb8607d:
---

>How-To-Repeat:
Start xdm on DomU (from /etc/rc.conf or commandline), 
start the X-Server and "query" for the DomU's xdm from Dom0:

     # X -query 192.168.1.3

xdm appears, type login and password - the DomU crashes!

xdm is configured for XDMCP, and the setup had worked before - before I changed to the most current netbsd-XEN3_DOM0 and netbsd-XEN3_DOMU kernels 




>Fix: