Re: [Xen-devel] dom0 kernel - irq nobody cared ... the continuing saga ..

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Monday, February 9, 2015, 5:36:28 PM, you wrote:

>>>> On 09.02.15 at 16:18, <david.vrabel@xxxxxxxxxx> wrote:
>> On 09/02/15 15:03, Sander Eikelenboom wrote:
>>> Hi Jan / David / Konrad,
>>> 
>>> I was just testing a 3.19 kernel on my intel machine and again
>>> ran into the sporadically appearing "irq nobody cared" on the dom0 kernel.
>>> This occurs now for quite some kernel versions (running xen-unstable now,
>>> but it also appeared in the past with builds that are now xen-4.5).
>> 
>> I wouldn't suspect anything Xen related here.  IRQ #18 is a shared
>> line-level interrupt so other driver/device that was/is sharing than
>> line is misbehaving.
>> 
>> I'd recommend seeing if your BIOS has a option to put the disk
>> controllers into AHCI mode which would allow them to use MSIs (I think).

> But iirc previous instances weren't always pointing at a disk
> controller, and hence dealing with that as a special case won't
> make the underlying problem go away.

> Sander, this looking different from previous reports of yours -
> is this different (or differently configured) hardware now? In
> which case knowing what other devices sit on that same IRQ
> would (again) be necessary, including which of them you pass to
> guests.

> Jan

S-ata controller is already in AHCI mode and using MSI, it actually was
the IDE controller that was on irq 18.

Yes the device that tries to handle the interrupt seems to change .. 
however that device is always not actively used.
This time it was an unused IDE controller with driver loaded in dom0
and a mini-pcie wifi card passed through to a guest.

But i did a bios update like David suggested and now the IDE controller
is gone (which is chipset only since it lacks a physical connector anyway).

Now it is sharing the IRQ with the SMbus:

00:1f.3 SMBus: Intel Corporation 7 Series/C210 Series Chipset Family SMBus 
Controller (rev 04)
        Subsystem: Intel Corporation Device 204f
        Flags: medium devsel, IRQ 18
        Memory at f7d35000 (64-bit, non-prefetchable) [size=256]
        I/O ports at f040 [size=32]

02:00.0 Network controller: Atheros Communications Inc. AR9285 Wireless Network 
Adapter (PCI-Express) (rev 01)
        Subsystem: Lenovo Device 30a1
        Flags: bus master, fast devsel, latency 0, IRQ 18
        Memory at f7c00000 (64-bit, non-prefetchable) [size=64K]
        Capabilities: [40] Power Management version 3
        Capabilities: [50] MSI: Enable- Count=1/1 Maskable- 64bit-
        Capabilities: [60] Express Legacy Endpoint, MSI 00
        Capabilities: [100] Advanced Error Reporting
        Capabilities: [140] Virtual Channel
        Capabilities: [160] Device Serial Number 00-00-00-00-00-00-00-00
        Capabilities: [170] Power Budgeting <?>
        Kernel driver in use: pciback

Why it seems so keen on interrupt sharing eludes me completely.

Also wondering why it doesn't enable MSI on the WIFI NIC, but perhaps the driver
doesn't support it .. will have to look at that later and see what it does when 
booting baremetal.

--
Sander



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