arm: DomU Networking enable leads to Dom0 kernel oops

* arm: DomU Networking enable leads to Dom0 kernel oops
@ 2020-04-24 20:29 Andrei Cherechesu
  2020-04-24 20:46 ` Julien Grall
  2020-04-25  2:01 ` Stefano Stabellini
  0 siblings, 2 replies; 6+ messages in thread
From: Andrei Cherechesu @ 2020-04-24 20:29 UTC (permalink / raw)
  To: Stefano Stabellini, Julien Grall; +Cc: xen-devel

[-- Attachment #1: Type: text/plain, Size: 3887 bytes --]

Hello,

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 8.8.8.8 works):
xenbr0    Link encap:Ethernet  HWaddr B2:62:37:C9:BB:D7
          inet addr:192.168.0.185  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::b062:37ff:fec9:bbd7/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          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
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          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
access
[  413.367873] Unable to handle kernel paging request at virtual address 000006c000020070
In
               [  413.548189]  xenvif_rx_ring_slots_available+0x40/0xa0 [xen_netback]

The full log is attached at [0]<https://pastebin.com/sJLfd4gL>.
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
access
               [ 5338.574809] Unable to handle kernel paging request at virtual address 000000c0ffff0028
in
               [ 5338.753128]  xenvif_tx_build_gops+0x528/0xef8 [xen_netback]

               The full log is attached at [1]<https://pastebin.com/iaF1q3UM>.
               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).
1269      #ifdef NET_SKBUFF_DATA_USES_OFFSET
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

[-- Attachment #2: Type: text/html, Size: 14293 bytes --]

^ permalink raw reply	[flat|nested] 6+ messages in thread