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

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Friday, September 26, 2014, 8:59:22 AM, you wrote:

>>>> On 26.09.14 at 00:09, <linux@xxxxxxxxxxxxxx> wrote:
>> - Tried booting dom0 with pci=nosmi, but that didn't make a difference, 
>> still 
>>   "irq16 nobody cared".
>> - Tried booting dom0 with pci=nomsi and irqpoll, that prevented the "irq16 
>>   nobody cared" from appearing, i could see around 600000 interrupts for 
>> irq16,
>>   however the machine now freezes shortly afterward without any error (on 
>> serial 
>>   console with sync-console on, triple ctrl-a also doesn't work anymore)

> Again please don't mix up host and guest MSI. Host IRQ 16 can't
> possibly be an MSI one.

The idea was trying to not use MSI's but intx .. to see if it makes a 
difference.

>> - Tried switching off the onboard soundcard in the bios. Now irq16 is not 
>> bound 
>>   to any device, but the machine still freezes without any error (on serial 
>>   console with sync-console on, triple ctrl-a also doesn't work anymore)

> I suppose that hang is with irqpoll still in use? Ctrl-a not working anymore
> makes me wonder whether you use a PCI serial card sitting on that same
> IRQ for the Xen console... 

With and without irqpoll in use. 
I'm using the onboard serial header, just checked and 
it's set in the bios to use irq4, it is however on the super i/o controller, 
which in turn is part of southbridge. 

That has a ioapic, super i/o (serial, fans, sensors), usb controller, and the 
soundcontroller (now gone but that was 14.2 with irq16).

00:14.0 SMBus: Advanced Micro Devices [AMD] nee ATI SBx00 SMBus Controller (rev 
41)
00:14.3 ISA bridge: Advanced Micro Devices [AMD] nee ATI SB7x0/SB8x0/SB9x0 LPC 
host controller (rev 40)
00:14.4 PCI bridge: Advanced Micro Devices [AMD] nee ATI SBx00 PCI to PCI 
Bridge (rev 40)
00:14.5 USB controller: Advanced Micro Devices [AMD] nee ATI SB7x0/SB8x0/SB9x0 
USB OHCI2 Controller

I don't know what happens if there is a race / ordering problem in say 
xen/iommu/pciback pulling 
the device from the guest on shutdown while there are still irq's pending ?

(the code of xen_pciback's release and resetting function for instance seems to 
do a different 
ordering compared to vfio-pci's)

> Furthermore in that mode (with supposedly no
> handler set up for IRQ 16) monitoring (with a little bit of debugging code)
> how/when IRQ 16 gets setup and unmasked may provide further hints.

I don't know if i made it clear enough, but without the device occupying irq16 
it doesn't give the irq16 nobody cared (or any such message or error), it just 
freezes.


> Jan




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