Re: [Xen-devel] Xen-unstable: pci-passthrough "irq 16: nobody cared" on HVM guest shutdown on irq of device not passed through.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 25.09.14 at 17:49, <linux@xxxxxxxxxxxxxx> wrote:

> Thursday, September 25, 2014, 5:11:33 PM, you wrote:
> 
>>>>> On 25.09.14 at 16:36, <linux@xxxxxxxxxxxxxx> wrote:
>>> - When shutting down the HVM guest when A happens the number of interrupts 
>>> in 
> 
>>> /proc/interrups is still what it was, but when B happens it seems like a 
>>> irq 
> 
>>> storm
>>>   and after the irq nobody cared that ends with (always that 200000 so 
>>> perhaps a threshold ?):
>>>   16:     200000          0          0          0          0          0  
> xen-pirq-ioapic-level  snd_hda_intel
> 
>> 100,000 is the traditional threshold, so I would expect the cited
>> instance to be the second one. It didn't really become clear to me
>> - is this observed in Dom0 or in the shutting down guest? 
> 
> This is from the /proc/interrupts of dom0 after the irq nobody cared message 
> appeared in dom0 (so after B happened). Just after host boot and first guest 
> boot it was stable around 500. On the next start (and after which B would 
> happen on shutting the guest down again) it doubled to about 1000 (perhaps 
> when 
> the "Unsupported MSI delivery mode 3 for Dom2" occured).

Something odd must then be going on - the threshold _is_ 100,000,
not 200,000.

>> And did you really check that no other device (even if currently not having
>> an interrupt handler bound) is sitting on IRQ 16?
> 
> In what way could i check that to be certain ?
> (if it's not bound, lspci and /proc/interrupts will probably be insufficient 
> for that ?)

If the BIOS sets these up, lspci might still be of help. Consulting
boot messages of the kernel may also provide some hints. Beyond
that I'm not really sure how to figure out.

Jan


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