Re: [Xen-devel] Dom 0 crash

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Tue, Nov 05, 2013 at 10:29:49PM +0000, Ian Murray wrote:
> On 05/11/13 13:16, Jan Beulich wrote:
> >>>>On 05.11.13 at 12:58, Ian Murray <murrayie@xxxxxxxxxxx> wrote:
> >>I have a recurring crash using Xen 4.3.1-RC2 and Ubuntu 12.04 as Dom0
> >>(3.2.0-55-generic). I have software RAID 5 with LVM's. DomU (also 12.04
> >>Ubuntu 3.2.0-55 kernel) has a dedicated logical volume, which is being 
> >>backed
> >>up shutting down the DomU, an LVM snapshot being created, restart of DomU 
> >>and
> >>then the snapshot dd'ed to another logical volume. The snapshot is then
> >>removed and the second LV is dd'ed to gzip and onto DAT tape.
> >>
> >>I currently have this running every hour (unless its already running) for
> >>testing purposes. After 6-12 runs of this, the Dom0 kernel crashes with he
> >>below output.
> >>
> >>When I preform this booting into the same kernel standalone, the problem
> >>does not occur.
> >Likely because the action that triggers this doesn't get performed
> >in that case?
> Thanks for the response.
> 
> I am obviously comparing apples and oranges, but I have tried to be
> as similar as possible in as much as I have limited kernel memory to
> 512M as I do with Dom0 and have used a background task writing
> /dev/urandom to the LV that the domU would normally be using. The
> only difference is that it isn't running under Xen and I don't have
> a domU running in the background. I will repeat the exercise with no
> domU running, but under Xen.
> 
> 
> >>Can anyone please suggest what I am doing wrong or identify if it is bug?
> >Considering that exception address ...
> >
> >>RIP: e030:[<ffffffff8142655d>]  [<ffffffff8142655d>] 
> >>scsi_dispatch_cmd+0x6d/0x2e0
> >... and call stack ...
> >
> >>[24149.786311] Call Trace:
> >>[24149.786315]  <IRQ>
> >>[24149.786323]  [<ffffffff8142da62>] scsi_request_fn+0x3a2/0x470
> >>[24149.786333]  [<ffffffff812f1a28>] blk_run_queue+0x38/0x60
> >>[24149.786339]  [<ffffffff8142c416>] scsi_run_queue+0xd6/0x1b0
> >>[24149.786347]  [<ffffffff8142e822>] scsi_next_command+0x42/0x60
> >>[24149.786354]  [<ffffffff8142ea52>] scsi_io_completion+0x1b2/0x630
> >>[24149.786363]  [<ffffffff816611fe>] ? _raw_spin_unlock_irqrestore+0x1e/0x30
> >>[24149.786371]  [<ffffffff81424b5c>] scsi_finish_command+0xcc/0x130
> >>[24149.786378]  [<ffffffff8142e7ae>] scsi_softirq_done+0x13e/0x150
> >>[24149.786386]  [<ffffffff812fb6b3>] blk_done_softirq+0x83/0xa0
> >>[24149.786394]  [<ffffffff8106fa38>] __do_softirq+0xa8/0x210
> >>[24149.786402]  [<ffffffff8166ba6c>] call_softirq+0x1c/0x30
> >>[24149.786410]  [<ffffffff810162f5>] do_softirq+0x65/0xa0
> >>[24149.786416]  [<ffffffff8106fe1e>] irq_exit+0x8e/0xb0
> >>[24149.786428]  [<ffffffff813aecd5>] xen_evtchn_do_upcall+0x35/0x50
> >>[24149.786436]  [<ffffffff8166babe>] xen_do_hypervisor_callback+0x1e/0x30
> >>[24149.786441]  <EOI>
> >>[24149.786449]  [<ffffffff810013aa>] ? hypercall_page+0x3aa/0x1000
> >>[24149.786456]  [<ffffffff810013aa>] ? hypercall_page+0x3aa/0x1000
> >>[24149.786464]  [<ffffffff8100a500>] ? xen_safe_halt+0x10/0x20
> >>[24149.786472]  [<ffffffff8101c913>] ? default_idle+0x53/0x1d0
> >>[24149.786478]  [<ffffffff81013236>] ? cpu_idle+0xd6/0x120
> >... point into the SCSI subsystem, this is likely the wrong list to
> >ask for help on.
> ... but the right list to confirm that I am on the wrong list? :)

:-)
> 
> Seriously, the specific evidence may suggest it's a non-Xen
> issue/bug, but Xen is the only measurable/visible difference so far.
> I referred it to this list because here the demarcation between
> hypervisor, PVOPS and regular kernel code interaction is likely best
> understood.

But you wouldn't do the same workload under baremetal thought?

Here is a thought.  If you just do: "LV is dd'ed to gzip and onto DAT tape."
for 15 times under baremetal do you see the same issue?

And is there something particular about this DAT? Is it just a generic
/dev/st device? 

Lastly, complete shot in the dark - try increasing the swiotlb size.
Do 'swiotlb=65543' on the Linux command line when booting under Xen.

> 
> Thanks again for your response.
> 
> >
> >Jan
> >
> 
> 
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