[vfio-users] Interrupt Handling: Regression or config change?

[Ede Wolf]

Hello Alex,


thanks very much for showing some interest. I have found an archive of 
older arch kernels and can confirm, the last working kernel is:

Linux kvmother 4.5.4-1-ARCH #1 SMP PREEMPT Wed May 11 22:21:28 CEST 2016 
x86_64 GNU/Linux

the next kernel release from the arch team would be according to the 
archive:

Linux kvmother 4.6.1-1-ARCH #1 SMP PREEMPT Thu Jun 2 07:17:31 CEST 2016 
x86_64 GNU/Linux

and this already does not work any more. Also crosschecked to 4.6.5-1, 
no change and of course none with 4.8.x either.

Installed and reinstalled both (4.5 and 4.6) multiple times, including 
power off and hard reset between kernels, and the results are 
absolutelty consistent.

Suggests, that either some bug or some required configuration change I 
am not aware of has been introduced with Kernel 4.6.

Unfortunately I do not know enough about programming at all to bring it 
down to a certain commit (not to look for that), but if there is 
anything I could do, just let me know. please.


Thanks again

Ede


Am 06.01.2017 um 00:30 schrieb Alex Williamson:
> On Thu, 5 Jan 2017 19:14:29 +0100
> Ede Wolf <listac at nebelschwaden.de> wrote:
>
>> Hello,
>>
>> Running arch, I am having a windows XP guest, to which I am passing
>> through a PCIe Parallel Card, that again talks to a device that
>> unfortunately is very picky about interrupts and more so the interrupt
>> setting within Windows XP for that parallel port.
>>
>> For a short explanation: Windows XP offers 3 ways to operate the
>> parallel port:
>> "never use an interrupt"
>> "try not to use an interrupt"
>> "Use any interrupt assigned to that port"
>>
>> My device requires the last option, otherwise communication does simply
>> not work, albeit the device itself is detected. So it seems, that
>> whatever setting I choose within windows xp, it is now ignored and does
>> not make any difference any more.
>>
>> However, it used to work perfectly fine up to Kernel 4.5. or 4.6, I do
>> not remember exactly, but does not work any more with 4.8. Skipped 4.7
>> for sure.
>>
>> Booting into the 4.4-lts kernel makes things work as expected, booting
>> into 4.8.x and communication is broken again. Can be repeated at will
>> with consistently the same results and holds true now for several
>> incarnations of the 4.8 kernel the archlinux team has provided so far.
>>
>> Now I am wondering: Is there any compelling configuration change that I
>> am not aware of or is this simply a bug? And if, is this related to vfio
>> or other parts of the kernel and this the wrong place?
>>
>> Thanks for any help
>
> Any chance you could narrow down where this broke a little further,
> perhaps even bisecting the kernel to a specific commit?  Thanks,
>
> Alex
>