Re: Custom kernel module woes

[Marius Bakke]

Thorsten Wilms  writes:

> Now if anyone knows or can figure out how *exactly* to turn XTS's -*- 
> into a {M}, that would still be good to know. A script that turns any 
> kernel configuration into a guix-sd-safe one, or changes to make these 
> gymnastics unnecessary would be great!

I recently revamped my kernel configuration and hit this issue too.  In
my case I had to disable ext4 encryption to build xts.ko as a module.

Perhaps we should build ext4 as a module in Guix?  Or make XTS a builtin?


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Re: Custom kernel module woes

[Thorsten Wilms]

On 22.03.2018 18:51, Marius Bakke wrote:


Can you post the .config that requires CONFIG_CRYPTO_XTS=y?


I attached the result of `make menuconfig` in linux-libre-4.15.12, as 
that shows the issue and is as neutral as it gets.




I remember having to turn on "expert" configuration in order to change
some of the default builtins.  If this is the case, perhaps we should
make it a built-in on GuixSD too.


It already has CONFIG_EXPERT=y, as interesting as that might seem as a 
default.



--
Thorsten Wilms

thorwil's design for free software:
http://thorwil.wordpress.com/


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Re: Custom kernel module woes

[Marius Bakke]

Thorsten Wilms  writes:

> Things were going well until I got to XTS support. With either my custom 
> configuration, or a default one, XTS is stuck on -*-, i.e. mandatory 
> built-in. The after-build phase will fail if there's no xts.ko module!
>
> I tried to figure out the dependencies and failed. Finally, I took the 
> guix kernel configuration, replaced the entire segment device-drivers up 
> to file-systems with one from my custom version and did the few other 
> changes. It works!
>
> Now if anyone knows or can figure out how *exactly* to turn XTS's -*- 
> into a {M}, that would still be good to know. A script that turns any 
> kernel configuration into a guix-sd-safe one, or changes to make these 
> gymnastics unnecessary would be great!

Can you post the .config that requires CONFIG_CRYPTO_XTS=y?

I remember having to turn on "expert" configuration in order to change
some of the default builtins.  If this is the case, perhaps we should
make it a built-in on GuixSD too.


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Custom kernel module woes

[Thorsten Wilms]

Hi!

My mentionable reasons for a custom kernel are optimizations for audio 
work (CONFIG_HZ=1000 and "Preemptible Kernel (Low-Latency Desktop)"), 
the specific CPU and reducing time and energy costs of building by 
selecting only the necessary drivers.


I added the package definition to my system configuration to then have 
the kernel build and put into place via `guix system reconfigure 
/ect/config.scm`. This failed several times after building, when guix 
does what I understand to be an initramfs test run, where it tries to 
load a bunch of modules.


With the help of #guix, I found a list that appears in 
linux-modules-builder and init-builder:
("ahci" "usb-storage" "uas" "usbhid" "hid-generic" "hid-apple" 
"dm-crypt" "xts" "serpent_generic" "wp512" "nls_iso8859-1" "pata_acpi" 
"pata_atiixp" "isci" "virtio_pci" "virtio_balloon" "virtio_blk" 
"virtio_net" "virtio_console")


Aside of the issue of requiring hid-apple on a desktop PC, and lots of 
crypto where no encrypted partition is in sight, it would be nice if an 
error could be triggered before the entire kernel and drivers are build.


My notes from hunting down these configuration dependencies:
ahci
dm-crypt, depends on:
  Multiple device driver support: Device mapper support: Crypt target 
support

  Cryptographic API: User-space interface for hash algorithms
 User-space interface for symmetric key cipher 
algorithms

 RIPEMD-160 digest algorithm
 SHA384 and SHA512 digest algorithms
 wp512 / Whirlpool digest algorithms
 LRW support
 serpent_generic / Serpent cipher algorithm
 Twofish cipher algorithm
  Device Drivers: Block Devices: Loopback device support
  File systems: FUSE (Filesystem in Userspace) support
hid-generic
hid-apple
isci
nls_iso8859-1
pata_acpi
pata_atiixp
uas, CONFIG_USB_UAS in Device Drivers, USB, USB Attached SCSI.
usb-storage
usbhid
virtio_pci
virtio_balloon
virtio_blk
virtio_net
virtio_console
xts


Things were going well until I got to XTS support. With either my custom 
configuration, or a default one, XTS is stuck on -*-, i.e. mandatory 
built-in. The after-build phase will fail if there's no xts.ko module!


I tried to figure out the dependencies and failed. Finally, I took the 
guix kernel configuration, replaced the entire segment device-drivers up 
to file-systems with one from my custom version and did the few other 
changes. It works!


Now if anyone knows or can figure out how *exactly* to turn XTS's -*- 
into a {M}, that would still be good to know. A script that turns any 
kernel configuration into a guix-sd-safe one, or changes to make these 
gymnastics unnecessary would be great!



A drawback of a lean and specific kernel is of course that it won't work 
with drastically changed hardware. A situation once can suddenly be 
forced into on hardware failure.


Kernel variants are tied to system generations, right? What do I have to 
do if I want a choice between 2 kernels independent of generations?



--
Thorsten Wilms

thorwil's design for free software:
http://thorwil.wordpress.com/