Re: NetBSD/xen goes off the network - reproduceable

[Brian Marcotte <marcotte%panix.com@localhost>]

> the attached patch changes xennet(4) to use a pool for receive
> buffer, and allocate them on demand for the ring. If a receive buffer
> is stalled in some socket queue, it's should not be a problem any more
> (other than memory consumption).

I applied the patch to NetBSD-6 and I can no longer provoke the problem
with my simple test.

Thanks!

However, running "tcpdump -i xennet0 -n icmp" reliably causes the panic
below after 1-15 seconds. There may be one other issue, but I'm going to
need another day to look into it. I think it may be something I'm doing.


fatal page fault in supervisor mode
trap type 6 code 0 eip c0108e36 cs 9 eflags 10287 cr2 506ff31 ilevel 8
kernel: supervisor trap page fault, code=0
Stopped in pid 0.2 (system) at  netbsd:m_xhalf+0x76:    movzwl  0(%edi),%esi
m_xhalf(c9ff3e38,c02c3c54,c0b08154,c1720900,4ce14000,4,c040f7c2,ee6b4000,c9ff3e38,c0ad1e7c)
 at netbsd:m_xhalf+0x76
bpf_filter(c16465b4,c0bd6000,0,0,1d00,100,ab1000,0,c03ab1c0,0) at 
netbsd:bpf_filter+0x2e0
_bpf_mtap(c0aba724,c1720900,c0ad02a4,c0409160,c9ff3eb0,c04091c4,c04091c0,0,4f43e1a5,c0acf018)
 at netbsd:_bpf_mtap+0xb0
xennet_handler(c0acf000,0,c0400f80,c065b000,e,c0aba4e0,c9ff3fe8,c013d15b,c0aba4e0,ca18ac80)
 at netbsd:xennet_handler+0x3d8
intr_biglock_wrapper(c0aba4e0,ca18ac80,0,c9ff3fec,c016aaf7,e,1,6,16a80,c055c458)
 at netbsd:intr_biglock_wrapper+0x1f
evtchn_do_event(e,ca18ac80,ca18abf8,0,0,0,0,0,0,0) at 
netbsd:evtchn_do_event+0x16b
--- switch to interrupt stack ---
call_evtchn_do_event(ca18ac80,0,c0b20011,c0400031,ca180011,c01f0011,c0b24d40,c0400f80,ca18acec,1)
 at netbsd:call_evtchn_do_event+0x1e
hypervisor_callback(c0b26d20,0,c01e0c0b,c0b26d20,0,0,0,ca18ada0,c0407ac0,c0b26d20)
 at netbsd:hypervisor_callback+0x64
idle_loop(c0b26d20,65a000,c055c200,0,c010006d,0,0,0,0,0) at 
netbsd:idle_loop+0x17c
ds          11
es          c0ad0011
fs          3fd0031
gs          c0640011
edi         506ff31
esi         0
ebp         c9ff3dc0
ebx         4060008
edx         e
ecx         c9ff3e18
eax         c0bd6000
eip         c0108e36    m_xhalf+0x76
cs          9
eflags      10287
esp         c9ff3db4
ss          11
netbsd:m_xhalf+0x76:    movzwl  0(%edi),%esi