Re: [Xen-devel] segfault in VM

[Derek Glidden <dglidden@xxxxxxxxxxxxxxx>]

On Jul 21, 2004, at 9:30 AM, Keir Fraser wrote:
> To disable networking:
> Edit arch/xen/drivers/netif/frontend/main.c. Change netif_init() to
> always 'return 0;'.
changing netif_init() so that all the returns are "return 0;" doesn't 
seem to do much, the VMs still get network access, and everything looks 
and acts normal and there's still corruption after a few minutes of 
stress testing and network traffic.  (Although it does seem to be 
network related.  It ran for a while with no network traffic and no 
corruption, and within a minute or two of starting the pings, it 
started to flake out.)
changing netif_init() so that it immediately does "return 0" runs for a 
good long time with no corruption, unless you try to send data to one 
of the vifs, which makes dom0 blow up real good. Running it for a while 
with just block I/o and ping traffic to dom0 didn't result in any 
obvious corruption while running, but I did get these messages when I 
rebooted:
(XEN) (file=/opt/src/xeno/xeno-unstable.bk/xen/include/asm/mm.h, 
line=215) Unexpected type (saw c0000000 != exp e0000000) for pfn 
000032db
(XEN) DOM0: (file=memory.c, line=249) Bad page type for pfn 000032db 
(d0000005)
(XEN) (file=traps.c, line=466) GPF (0004): fc5277c8 -> fc52a094
Kernel panic: Failed to execute MMU updates
 (XEN) Domain 0 shutdown: rebooting machine!

which I've only seen on a reboot when there has been corruption.

disabling the receive path seems to still let packets through and shows 
signs of corruption, even with very little network traffic.  I'm not 
sure if that's because I have everything doing NAT instead of bridging, 
although that doesn't really make sense since it's still the same 
interface and the code looks like it should simply drop the packets...
It's getting late so I'll have to work on disabling the transmit path 
and working out how to go about testing the blockdev backend tomorrow.
I'll let it run for a while without even up'ing the vifs on the dom0 
side, which should preclude any network traffic at all getting to the 
VMs and see if there's any corruption going on running overnight or 
longer.
Can anyone else corrupt their systems with no network traffic?

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