Re: 4.4-rc3, KVM, br0 and instant hang

On 12/05/2015 10:31 AM, John Stoffel wrote:

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"John" == John Stoffel [off-list ref] writes:

John> On Fri, Dec 04, 2015 at 11:28:33PM -0500, John Stoffel wrote:

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Hi all,

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Anyway, if I try to boot up anything past the 4.2.6 kernel, the system
locks up pretty quickly with an oops message that scrolls off the
screen too far.  I've got some pictures which I'll attach in a bit,
maybe they'll help.  So at first I thought it was something to do with
bad kworker threads, or SCSI or SATA interactions, but as I tried to
configure Netconsole to log to my beaglebone black SBC, I found out
that if I compiled and installed 4.4-rc3, started the bridge up (br0),
even started KVM, but did NOT start my VMs, the system was stable.

I've now figured out that I can disable all my VMs from autostart, and
the system will come up properly.  Then I can setup netconsole to use
the br0 interface, do an  "echo t > sysrq" to confirm it's working,
and start up the VMs.

On my most recent bootup, I thought it was ok, since the VMs worked
for a while (10 minutes) and I was starting to re-compile the kernel
again to make more modules compiled in.  No luck, I got the following
crash dump (partial) on my netconsole box.

[ 1434.266524] ------------[ cut here ]------------
[ 1434.266643] WARNING: CPU: 2 PID: 179 at block/blk-merge.c:435 blk_rq_map_sg+0x2d9/0x2eb()

This is fixed in current -git, as of a few days ago.

-- 
Jens Axboe