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arm: DomU Networking enable leads to Dom0 kernel oops

  • To: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>
  • From: Andrei Cherechesu <andrei.cherechesu@xxxxxxx>
  • Date: Fri, 24 Apr 2020 20:29:53 +0000
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  • Thread-topic: arm: DomU Networking enable leads to Dom0 kernel oops



Recently I’ve been trying to enable the networking in a conventional DomU (not dom0less).

The approach I used was the one described here: https://wiki.xen.org/wiki/Xen_Networking#Bridging.


But when I use xl to create DomU, I get a Kernel OOPS in Dom0. The setup is still responsive after this

and DomU boots successfully. However, if I try to enable `eth0` in DomU (using ip link dev set eth0 up),

I get a Kernel Panic in Dom0.


Here are the complete steps:

  1. Boot Dom0 and configure bridge:
    • brctl addbr xenbr0
    • brctl addif xenbr0 eth0
    • ip link set dev xenbr0 up
    • ip link set dev eth0 up
    • dhclient xenbr0


  1. ifconfig xenbr0 (ping works):

xenbr0    Link encap:Ethernet  HWaddr B2:62:37:C9:BB:D7

          inet addr:  Bcast:  Mask:

          inet6 addr: fe80::b062:37ff:fec9:bbd7/64 Scope:Link


          RX packets:703 errors:0 dropped:0 overruns:0 frame:0

          TX packets:27 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:1000

          RX bytes:88213 (86.1 KiB)  TX bytes:3088 (3.0 KiB)


  1. ifconfig eth0:

eth0      Link encap:Ethernet  HWaddr B2:62:37:C9:BB:D7 

          inet6 addr: fe80::b062:37ff:fec9:bbd7/64 Scope:Link


          RX packets:1535 errors:0 dropped:2 overruns:0 frame:0

          TX packets:43 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:1000

          RX bytes:450476 (439.9 KiB)  TX bytes:4248 (4.1 KiB)

          Interrupt:59 Base address:0xc000


  1. Add bridge to DomU config file:

vif = [ 'bridge=xenbr0' ]


  1. root@s32g274aevb-Dom0:~# xl create /etc/xen/domU1.cfg

After this I get the Kernel OOPS, because of a failed memory


[  413.367873] Unable to handle kernel paging request at virtual address 000006c000020070


               [  413.548189]  xenvif_rx_ring_slots_available+0x40/0xa0 [xen_netback]


The full log is attached at [0].

Using gdb, I found out that the access corresponds to the following source code lines:


               (gdb)  l *xenvif_rx_ring_slots_available+0x40

0x65b0 is in xenvif_rx_ring_slots_available (/usr/src/kernel/include/linux/skbuff.h:4084).

4082      static inline bool skb_is_gso(const struct sk_buff *skb)

4083      {

4084                     return skb_shinfo(skb)->gso_size;

4085      }



  1. DomU boots, and then: root@s32g274aevb-DomU1:~# ip link set dev eth0 up

After this, I get a kernel panic in Dom0 because of another failed memory


               [ 5338.574809] Unable to handle kernel paging request at virtual address 000000c0ffff0028


               [ 5338.753128]  xenvif_tx_build_gops+0x528/0xef8 [xen_netback]


               The full log is attached at [1].

               Using gdb again, I found out the corresponding source code:


(gdb) l *xenvif_tx_build_gops+0x528

0xce8 is in xenvif_tx_build_gops (/usr/src/kernel/include/linux/skbuff.h:1272).


1270      static inline unsigned char *skb_end_pointer(const struct sk_buff *skb)

1271      {

1272                     return skb->head + skb->end;

1273      }



Do you have any idea why this occurs? Have I misconfigured anything?


I’ve also tried to pass a static IP configuration for DomU in the config file,

and because it automatically enables eth0 at boot time, I no longer get the

oops, but a panic directly.


Thank you very much for your help,

Andrei Cherechesu,

NXP Semiconductors



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