Re: [Xen-devel] 3.19-rc4: Xen pci-passthrough regression, bisected to commit cffe0a2b5a34c95a4dadc9ec7132690a5b0f6687 "x86, irq: Keep balance of IOAPIC pin reference count"

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Wednesday, January 14, 2015, 3:58:33 PM, you wrote:

> On 14/01/15 14:15, Sander Eikelenboom wrote:
>> Hi Gerry / David / Konrad,
>> 
>> Some more testing uncovered another issue under Xen, this time with 
>> PCI-passthrough.

> What device?  In particular what interrupts is it using?

Hi David,

Here is a more complete set of debug logs, for both with and without the revert.
- dmesg
- xl-dmesg with output of debug keys 'i, M, z'
- lspci part of the two devices from the guest
- /proc/interrupts

The wifi NIC (dom0: 02:00.0 guest: 00:05.0) uses legacy interrupts and gives 
troubles:
It's using:
        Interrupt: pin A routed to IRQ 36
        Capabilities: [50] MSI: Enable- Count=1/1 Maskable- 64bit-
        36:      14413  xen-pirq-ioapic-level  ath9k

The other NIC (dom0: 00:19.0 guest: 00:06.0) uses MSI interrupts and that works 
fine:
        Interrupt: pin A routed to IRQ 57
        Capabilities: [d0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        57:        182  xen-pirq-msi       eth0
--
Sander  

>> I have bisected it to the following commit: 
>> cffe0a2b5a34c95a4dadc9ec7132690a5b0f6687 "x86, irq: Keep balance of IOAPIC 
>> pin reference count"
>> 
>> It causes these symptoms:
>> 
>> - On Intel
>>   - Running on Xen with pci devices seized on host boot with 
>> xen-pciback.hide= parameter
>>   - Running a HVM guest with PCI passthrough of two devices (NIC + wireless 
>> NIC)
>>   - While the driver loads fine, the device isn't working properly, looking 
>> in /proc/interrupts in the guest
>>     shows that it doesn't receive any interrupts.
>>   - Reverting this particular commit (in the dom0 kernel only) makes the 
>> device receive interrupts and work properly again.
>> 
>> - On AMD (more subtle symptom) 
>>   - Running on Xen with pci devices seized on host boot with 
>> xen-pciback.hide= parameter
>>   - Running a HVM guest with PCI passthrough of one devices (videograbber)
>>   - While the driver loads fine and the device looks like it's working, the 
>> videostream isn't stable and it skips or repeats frames.
>>   - Reverting this particular commit (in the dom0 kernel only) makes the 
>> device work properly again with a stable videostream.
>> 
>> --
>> Sander
>>

Attachment: dmesg.txt
Description: Text document

Attachment: dmesg-revert.txt
Description: Text document

Attachment: lspci-guest.txt
Description: Text document

Attachment: lspci-guest-revert.txt
Description: Text document

Attachment: proc-interrupts.txt
Description: Text document

Attachment: proc-interrupts-revert.txt
Description: Text document

Attachment: xl-dmesg.txt
Description: Text document

Attachment: xl-dmesg-revert.txt
Description: Text document

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