Meta issue about kernel configuration

[teto]

This issue lists steps I intend to follow to improve kernel integration into nixos.
Mainly I would like nixpkgs to be able to mark kernel configuration entries as dependencies.
For instance enabling bcc, should enable CONFIG_BPF or at least check that it is available.
Ideally I would like to make it easier to compose/override kernel configurations as the current process
is quite tricky (you gotta choose carefully between override/overrideAttrs).

• check the generated kernel config against the specified/requested config (really check requiredKernelConfig #69013)
• replace the perl code to check the config

  nixpkgs/pkgs/os-specific/linux/kernel/generate-config.pl

  Line 124 in e598c40

  my %config;

  with lib.kernel.loadConfig.
• enforce structuredConfig (get rid of configuration as strings ? rename extraStructruredConfig to extraConfig)
• let derivations specify their kernel dependencies (via meta hints as in system.requiredKernelConfig: packages contraints #55755 ? a specific type of derivation in propagatedBuildInputs ?)
• build a config that respects package dependencies. Might be very tricky but at least check the final config

Related issues:
#41103
#2296
#20187

[edolstra]

The problem with this is that there is no way to validate the kernel feature requirements specified by modules. For example, if a module requires BPF but doesn't declare it, it will still work correctly if BPF is enabled by some other module.

[teto]

One of my propositions is to tie the kernel requirement to the package (via meta.requiredKernelConfiguration for instance). Several packages can't be run without the proper kernel features (openvswitch/bpf/perf/mininet/powertop...).

Regarding your comment, if you just install this specific module and it doesn't declare its (required) dependency on BPF then you are screwed (in the absence of the other module) so you better declare it :p

[stale]

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