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

Tue Jan 10 02:46:40 UTC 2017

Hi Ede,    Found a small typo, the below command should be "git describe --tags".    The bisecting is as easy as compiling a pkg :)

>Check which version you are now:
>git --describe tags  

Regards,Daimon 

    On Sunday, January 8, 2017 1:40 AM, Manuel Ullmann <ullman.alias at posteo.de> wrote:

 Hello Ede,

you do not need to be a programmer for bisecting. It is just required,
that you can follow a step-by-step guide and adapt examples for your
case. Git documentation is quite good and the first time I bisected
something, I didn’t even know about it, but knew the git command for
jumping through the commit history, which was also sufficient, but more
time intensive. So:

mkdir /path/to/your/new/source
cd /path/to/your/new/source
git init
git remote add linux-stable git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
The following will just fetch the tags inbetween the versions you have
found, sparing you a lot disk space and download bandwidth.
git fetch linux-stable refs/tags/v4.5.4:refs/tags/v4.6.1

https://wiki.archlinux.org/index.php/Kernels/Traditional_compilation
Cherrypicked the Archwiki for the following:

Install build requirements:
pacman -S base-devel xmlto docbook-xsl kmod inetutils bc

Copy your current kernel configuration:
zcat /proc/config.gz > .config

Back to business: You should now have build tools and a configuration
available.

git bisect start
git bisect bad v4.5.4
git bisect good v4.6.1

git will now checkout a commit inbetween this range, which requires that
you repeat the following steps:

make olddefconfig
make -j<number-of-processor-cores> -l<number-of-processor-cores>.0
make modules_install
mount /boot (if required)
make install

Check which version you are now:
git --describe tags

mkinitcpio -g /boot/initramfs-<kernel major and minor versions>.img -k <kernel version without v>
(Example for 4.5.4:
mkinitcpio -g /boot/initramfs-45.img -k 4.5.4)

grub-mkconfig -o /boot/grub/grub.cfg
sudo systemctl reboot (or su -c 'systemctl reboot' if sudo is not installed)

If the version works, cd to the kernel source again and do
git bisect good
otherwise
git bisect bad

Repeat the above steps from make olddefconfig.
Bisect will print how much steps are left. Once it is finished it will
print out the commit.

Best regards,
Manuel
> 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
>>
>
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