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Date: Mon, 20 Aug 2018 11:49:04 +0200
From: Roger Pau =?utf-8?B?TW9ubsOp?= <roger.pau@citrix.com>
To: Marko Zec <zec@fer.hr>
CC: Nathan Friess <nathan.friess@gmail.com>, <freebsd-xen@freebsd.org>
Subject: Re: xen+vimage kernel panic
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On Sun, Aug 19, 2018 at 10:48:52PM +0200, Marko Zec wrote:
> On Sun, 19 Aug 2018 12:50:55 -0600
> Nathan Friess <nathan.friess@gmail.com> wrote:
> 
> > Hi,
> > 
> > While testing out the new PVH support in a domU (which is running 
> > great!), I discovered a kernel panic related to xen and vimage
> > support when trying to add an xn interface into a bridge.
> > 
> > I'm running r337024 from svn.  Removing vimage (which seems to be
> > turned on in 12-CURRENT now) allows using the bridge with no panics.
> > As part of attempting to debug this I enabled vimage in my 11.2 domU
> > and that also panics in the same code.
> > 
> > I'm not sure if the problem is a xen issue or a vimage issue so I 
> > haven't submitted a PR yet.  The kernel output is listed below.
> > 
> > It looks like netfront_backend_changed() calls
> > netfront_send_fake_arp(), which calls arp_ifinit() on the interface.
> > The first line of the call stack with arprequest+0x454 corresponds to
> > a call to ARPSTAT_INC(txrequests) at the end of arprequest, which
> > expands to VNET_PCPUSTAT_ADD().  I tried to debug further and I got a
> > little lost, but that's where I figured out that vimage is involved
> > somehow.
> > 
> > Are there any thoughts on why the xn interface would cause a panic
> > there?
> 
> The xn driver calls arp_ifinit() without setting the vnet context
> first.  Perhaps the attached patch could help (not even compile
> tested...)

I know nothing about VNET, so is this initialization required now that
VNET is enabled? Is this an existing bug in netfront that was harmless
before VNET was activated?

Can you please file a bug report and attach the patch?

Thanks, Roger.