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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.02.15 at 18:13, <linux@xxxxxxxxxxxxxx> wrote:
> 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.

Coming back to the /proc/interrupts output you posted earlier:

/proc/interrupts shows the high count:

           CPU0       CPU1       CPU2       CPU3
  8:          0          0          0          0  xen-pirq-ioapic-edge  rtc0
  9:          1          0          0          0  xen-pirq-ioapic-level  acpi
 16:         29          0          0          0  xen-pirq-ioapic-level  
ehci_hcd:usb3
 18:     200000          0          0          0  xen-pirq-ioapic-level  
ata_generic

I would have thought that xen-pciback would install an interrupt
handler here too when a device using IRQ 18 gets handed to a
guest. May there be something broken in xen_pcibk_control_isr()?

> 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.

Did you check whether the respective driver is capable of using
MSI?

Jan


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