Bug#983357: Bug#988776: Bug#983357: Netinst crashes xen domU when loading kernel

[Chuck Zmudzinski]

On 8/25/2021 4:16 PM, Phillip Susi wrote:
> Chuck Zmudzinski <brchuckz at netscape.net> writes:
>> If it doesn't work, I am also willing to try approach a by patching
>> the Linux kernel xen-kbdfront driver by removing the for loops that
>> advertise those 654 keys. I tend to agree with Philip that this is
>> totally unnecessary, but I suppose I could be wrong about that.
>> I read the discussion Philip had with the Xen developers and they
>> seemed to want to keep the Xen keyboard driver as it is.
> That was the first thing I tried and the libinput maintainer pointed out
> that if you don't advertise the keys, you can't use the keys.  In other
> words, somebody presses that key on their keyboard and the domU won't
> recognize it.
>

Well, good news - It looks like Ben's patch works, I just tested it in 
my full
install in a Xen HVM domU and all looks good. I did not see the Coldplug
failure at the beginning of the boot - it is hard to miss in the bright red
letters on the console, and even more convincing is the fact that another
symptom of the bug is gone. This bug manifests itself in udev not being
able to write uevent data to sysfs for the Xen Virtual Keyboard. With
Ben's patch of increasing the UEVENT_BUFFER_SIZE from 2048 to 4096,
udev can write its uevent data to sysfs for the Xen Virtual Keyboard:

With the current 5.10.0-8 kernel:

chuckz at debian:~$ cat /sys/devices/virtual/input/input2/uevent
chuckz at debian:~$

With the patched kernel with a change to the ABI version from 8 to 8.1:

chuckz at debian:~$ uname -r
5.10.0-8.1-amd64
chuckz at debian:~$ cat /sys/devices/virtual/input/input2/uevent
PRODUCT=1/5853/ffff/0
NAME="Xen Virtual Keyboard"
PHYS="xenbus/device/vkbd/0"
PROP=0
EV=3
KEY=7fffffffffffffff ffffffffffffffff ffffffffffffffff...
MODALIAS=input:b0001v5853pFFFFe0000-e0,1,k71,72... really long MODALIAS

I expect with that patch the installation media will work
in a Xen HVM domU.

Cheers,

Chuck