[Xen-users] problems using domu as network backend domain (fedora 7)

["Stefanie Braun" <fannys@xxxxxxx>]

Hello,

want to make a network setting where a domu acts as a network backend domain (domu1).
But the start of another domu (domu2) with its backend directed to domu1 causes a kernel bug at domu1.

The bug occurs in the netback/interface.c file. 
Anyhow the vif of domu2 is created correctly and visible via ifconfig in domu1. No errors visible  
in the xen log files. But after configuring correct ip and mac addresses no connection can be established
between both domus.

I think the bug occurs when the domu1 tries to map the frontend pages of domu2 into its address space.
Maybe domu1 is not privileged enough for the operation. 

Does anyone have the same problems? Any help appreciated.

Thank you.
Regards Fannys

fedora xen version: 2.6.21-6.fc7xen

domu1 config file:
bootloader = "/usr/bin/pygrub"
memory     = 1024
name       = "domu1"
vcpus     = 1
netif    = "yes"
vif        = [ 'mac=00:16:3e:26:96:d6,bridge=eth0,script=vif-bridge']
vnc        = 1
disk   = [ 'tap:aio:/var/lib/xen/images/xenshare/domu1.img,xvda,w']

domu2 config file:
bootloader = "/usr/bin/pygrub"
memory = 1024
name   = "domu2"
vcpus = 1
vif    = [ 'mac=00:16:3e:26:96:d7, backend=domu1, script=vif-nothing']
vnc    = 1
disk   = [ 'tap:aio:/var/lib/xen/images/xenshare/domu2.img,xvda,w']

my steps: starting domu1, doing modprobe netbk, (backend of domu1 is domain-0)
                starting domu2 (backend of domu2 is domu1)



Bug occurs in the netback/interface.c file in method map_frontend_pages on calling HYPERVISOR_grant_table_op(..)

eth0: no IPv6 routers present
------------[ cut here ]------------
kernel BUG at drivers/xen/netback/interface.c:204!
invalid opcode: 0000 [#1]
SMP 
last sysfs file: /class/net/vif7.0/address
Modules linked in: netbk(U) autofs4(U) hidp(U) l2cap(U) bluetooth(U) sunrpc(U) xennet(U) ipv6(U) dm_mirror(U) dm_multipath(U) dm_mod(U) parport_pc(U) lp(U) parport(U) loop(U) pcspkr(U) joydev(U) xenblk(U) ext3(U) jbd(U) mbcache(U) ehci_hcd(U) ohci_hcd(U) uhci_hcd(U)
CPU:    0
EIP:    0061:[<ee3e6c77>]    Not tainted VLI
EFLAGS: 00010286   (2.6.21-6.fc7xen #1)
EIP is at netif_map+0x9f/0x217 [netbk]
eax: ffffffff   ebx: 00000000   ecx: c23e5ef0   edx: 00000001
esi: ec998480   edi: c23e5ef0   ebp: 00000300   esp: c23e5ee0
ds: 007b   es: 007b   fs: 00d8  gs: 0000  ss: 0069
Process xenwatch (pid: 9, ti=c23e5000 task=ed7c25d0 task.ti=c23e5000)
Stack: 00000000 ecdd4a80 00000035 00000301 ee206000 00000000 00000002 00000300 
       00000007 ecd84c00 ecdd47a4 c11545da 00000009 ecd84c00 ecdd47a4 ee3ea1e8 
       ee3e629c 00000009 ece5eac0 ee3e70bb ee3e7089 c23e5f60 ee3e7020 ee3e701c 
Call Trace:
 [<c11545da>] xenbus_scanf+0x1d/0x53
 [<ee3e629c>] frontend_changed+0x348/0x598 [netbk]
 [<c11553f8>] otherend_changed+0x7b/0x80
 [<c1153d6a>] xenwatch_handle_callback+0x12/0x41
 [<c1154798>] xenwatch_thread+0xf6/0x10c
 [<c1153d58>] xenwatch_handle_callback+0x0/0x41
 [<c10342a9>] autoremove_wake_function+0x0/0x35
 [<c11546a2>] xenwatch_thread+0x0/0x10c
 [<c10341e0>] kthread+0xb0/0xd8
 [<c1034130>] kthread+0x0/0xd8
 [<c100598f>] kernel_thread_helper+0x7/0x10
 =======================
Code: 89 54 24 14 8d 7c 24 10 31 db 66 89 4c 24 20 ba 01 00 00 00 89 f9 c7 44 24 18 02 00 00 00 89 6c 24 1c e8 0d a6 c1 d2 85 c0 74 04 <0f> 0b eb fe 66 8b 44 24 22 66 85 c0 75 6d 8b 44 24 24 31 d2 89 
EIP: [<ee3e6c77>] netif_map+0x9f/0x217 [netbk] SS:ESP 0069:c23e5ee0
vif7.0: no IPv6 routers present
Bridge firewalling registered
ip_tables: (C) 2000-2006 Netfilter Core Team
Netfilter messages via NETLINK v0.30.
nf_conntrack version 0.5.0 (8192 buckets, 65536 max)
virbr0: no IPv6 routers present
vif7.0: no IPv6 routers present

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