linux-kernel - Re: netconsole regression w/ 8d8fc29d

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Message-ID: <20110615141641.GB23465@hmsreliant.think-freely.org>
Date:	Wed, 15 Jun 2011 10:16:41 -0400
From:	Neil Horman <nhorman@...hat.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	Cong Wang <amwang@...hat.com>,
	Linux kernel Mailing List <linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: netconsole regression w/ 8d8fc29d

On Wed, Jun 15, 2011 at 10:05:54AM -0400, Rik van Riel wrote:
> On 06/15/2011 04:10 AM, Cong Wang wrote:
> >于 2011年06月15日 15:58, Rik van Riel 写道:
> >>After commit 8d8fc29d02a33e4bd5f4fa47823c1fd386346093
> >>(netpoll: disable netpoll when enslave a device), it is
> >>no longer possible to use netconsole together with bridged
> >>KVM guests.
> >>
> >>I can see why the change looked reasonable from a networking
> >>point of view, but this has completely disabled netconsole
> >>functionality for a common KVM use case.
> >>
> >>After the change, netconsole refuses to bind to eth0.
> >>
> >>Since the bridge interface does not support polling,
> >>netconsole cannot use that, either.
> >
> >
> >Bridge does support polling now. :) You can just setup
> >netconsole on a bridge device.
> 
> This turns out to be mutually exclusive with attaching
> virtual interfaces (for KVM guests) to a bridge.
> 
> If I start netconsole first, my KVM guests won't start.
> 
> If I start the KVM guests first, netconsole won't start,
> and fails with these errors:
> 
> netconsole:: inserting netconsole module with arguments
> netconsole=6666@...92.59.68/br0,514@...92.59.66/00:13:72:17:4A:9C
> kernel: [ 1020.927240] netconsole: local port 6666
> kernel: [ 1020.927243] netconsole: local IP 74.92.59.68
> kernel: [ 1020.927245] netconsole: interface 'br0'
> kernel: [ 1020.927246] netconsole: remote port 514
> kernel: [ 1020.927247] netconsole: remote IP 74.92.59.66
> kernel: [ 1020.927252] netconsole: remote ethernet address 00:13:72:17:4a:9c
> kernel: [ 1020.927256] (null):  doesn't support polling, aborting.
> kernel: [ 1020.927258] netconsole: cleaning up
> systemd[1]: netconsole.service: control process exited, code=exited status=1
> systemd[1]: Unit netconsole.service entered failed state.
> 
> In short, I am still not able to use netconsole and bridged
> KVM guests at the same time...
> 
> # brctl show
> bridge name	bridge id		STP enabled	interfaces
> br0		8000.0024e838995c	no		eth0
> 							vnet0
> 							vnet1
> 							vnet2
> 
> 
> -- 
> All rights reversed

Looks like we need to teach the tun-tap driver to support netpoll that shouldn't
be too hard.  I'll send up a patch shortly
Neil

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