Re: [Xen-devel] PV DomU running linux 3.17.3 causing xen-netback fatal error in Dom0

[Anthony Wright <anthony@xxxxxxxxxxxxxxx>]

> On 01/12/14 14:22, David Vrabel wrote:
> This VIF protocol is weird. The first slot contains a txreq with a
> size
> for the total length of the packet, subsequent slots have sizes for
> that
> fragment only.
> 
> netback then has to calculate how long the first slot is, by
> subtracting
> all the size from the following slots.
> 
> So something has gone wrong but it's not obvious what it is. Any
> chance
> you can dump the ring state when it happens?

We think we've worked out how to dump the ring state, please see below.

dmesg output
============
[76571.687014] vif vif-6-0 vif6.0: txreq.offset: a5e, size: 4002, end: 6656
[76571.687035] vif vif-6-0 vif6.0: fatal error; disabling device
[76571.700304] br-primary-1: port 2(vif6.0) entered disabled state

/sys/kernel/debug/xen-netback/vif6.0/io_ring_q0
===============================================
Queue 0
TX: nr_ents 256
req prod 10164 (39) cons 10127 (2) event 10126 (1)
rsp prod 10125 (base) pvt 10125 (0) event 10145 (20)
pending prod 9589 pending cons 9333 nr_pending_reqs 0
dealloc prod 8501 dealloc cons 8501 dealloc_queue 0

RX: nr_ents 256
req prod 1321 (41) cons 1280 (0) event 1 (-1279)
rsp prod 1280 (base) pvt 1280 (0) event 1281 (1)

NAPI state: 1 NAPI weight: 64 TX queue len 0
Credit timer_pending: 0, credit: 18446744073709551615, usec: 0
remaining: 18446744073678062682, expires: 0, now: 4314107964


/sys/kernel/debug/xen-netback/vif6.0/io_ring_q1
===============================================
Queue 1
TX: nr_ents 256
req prod 10106 (0) cons 10106 (0) event 10107 (1)
rsp prod 10106 (base) pvt 10106 (0) event 10107 (1)
pending prod 9573 pending cons 9317 nr_pending_reqs 0
dealloc prod 8503 dealloc cons 8503 dealloc_queue 0

RX: nr_ents 256
req prod 594 (39) cons 555 (0) event 1 (-554)
rsp prod 555 (base) pvt 555 (0) event 556 (1)

NAPI state: 1 NAPI weight: 64 TX queue len 0
Credit timer_pending: 0, credit: 18446744073709551615, usec: 0
remaining: 18446744073678038030, expires: 0, now: 4314118667


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