Xen project Mailing List

On Fri, Apr 26, 2013 at 05:21:06AM +0100, Steven Haigh wrote:
> On 26/04/2013 1:36 AM, Wei Liu wrote:
> > On Thu, Apr 25, 2013 at 4:11 PM, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> >> On Thu, Apr 25, 2013 at 12:24:22PM +0100, Steven Haigh wrote:
> >>> Hi all,
> >>>
> >>> I've noticed a couple of DomUs have networking freeze with the following
> >>> getting printed to the Dom0's /var/log/messages:
> >>>
> >>> Apr 25 12:09:25 hosting kernel: vif vif-4-0 vif.crc: Frag is bigger than
> >>> frame.
> >>> Apr 25 12:09:25 hosting kernel: vif vif-4-0 vif.crc: fatal error;
> >>> disabling device
> >>> Apr 25 12:09:25 hosting kernel: br0: port 5(vif.crc) entered disabled 
> >>> state
> >>>
> >>> I thought this was something to do with MAX_SKB_FRAGS - however the
> >>> kernel I use has this increased to 19 - so in theory I shouldn't hit
> >>> this (as far as I know).
> >>>
> >>> Are there any other things that could trigger this?
> >>>
> >>
> >> You're seeing a netfront bug which is fixed in that series. And it is
> >> not related to MAX_SKB_FRAGS but related to GSO.
> >>
> >> Could you try applying my patch set "Bundle fixes for Xen netfront /
> >> netback" version 7. That series has been applied to DaveM's net-next.
> >>
> >
> > BTW with that series you should be able to get rid of the
> > MAX_SKB_FRAGS -> 19 hack.
> 
> This could be quite difficult. The DomU kernel is RHEL based - and not 
> easily changed without sending the patch upstream to RH - which may or 
> may not apply it.
> 
> My google-fu has failed a little here - do you have a link to the 
> patches? Is it against Xen or the kernel? Further, is it something that 
> just altering the Dom0 part would resolve?
> 

They are for Linux kernel only. Xen is not involved.

To get rid of your MAX_SKB_FRAGS hack, you need to patch Dom0 only.

To fix "Frag is bigger than frame", you need to patch DomU. If that's
not possible at the moment, I remember seeing a thread about disabling
guest GSO can workaround ths problem. You can give it a shot.


Wei.

> -- 
> Steven Haigh
> 
> Email: netwiz@xxxxxxxxx
> Web: https://www.crc.id.au
> Phone: (03) 9001 6090 - 0412 935 897
> Fax: (03) 8338 0299

Wei,

we just hit this bug as well on CentOS 5.9 with kernels 2.6.18-348.4.1.el5 and 2.6.18-348.6.1.el5, however I checked it on all domUs and dom0s GSO is off, only TSO is on. Would TSO still cause this issue?

Alex

Re: [Xen-devel] Frag is bigger than frame.