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linux/common-config.nix: disable LPAE on armv7l-linux #132100

Merged
merged 1 commit into from
Jul 30, 2021
Merged

linux/common-config.nix: disable LPAE on armv7l-linux #132100

merged 1 commit into from
Jul 30, 2021

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lopsided98
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Motivation for this change

LPAE was enabled to support (in the future, not yet implemented) native armv7l builders running in QEMU on aarch64, but this option disables support for processors which don't support LPAE, which are still relatively common. In particular, Beaglebones use the Cortex-A8, which doesn't support LPAE.

Also, if you attempt to boot an LPAE kernel on a CPU that doesn't support it, it fails before even earlycon is initialized. This makes the problem difficult to debug without enabling CONFIG_DEBUG_LL or using a hardware debugger.

cc @samueldr

Things done
  • Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
  • Built on platform(s)
    • NixOS
    • macOS
    • other Linux distributions
  • Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
  • Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
  • Tested execution of all binary files (usually in ./result/bin/)
  • 21.11 Release Notes (or backporting 21.05 Relase notes)
    • (Package updates) Added a release notes entry if the change is major or breaking
    • (Module updates) Added a release notes entry if the change is significant
    • (Module addition) Added a release notes entry if adding a new NixOS module
  • Fits CONTRIBUTING.md.

@lopsided98
linux/common-config.nix: disable LPAE on armv7l-linux
988c12f 
LPAE was enabled to support native armv7l builders running in QEMU on aarch64,
but this option disables support for processors which don't support LPAE, which
are still relatively common. In particular, Beaglebones use the Cortex-A8, which
doesn't support LPAE.

Also, if you attempt to boot an LPAE kernel on a CPU that doesn't support it,
it fails before even earlycon is initialized. This makes the problem difficult
to debug without enabling CONFIG_DEBUG_LL or using a hardware debugger.
@github-actions github-actions bot added the 6.topic: kernel The Linux kernel label Jul 30, 2021
@lopsided98 lopsided98 mentioned this pull request Jul 30, 2021
Merged
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@ofborg ofborg bot added 10.rebuild-darwin: 0 This PR does not cause any packages to rebuild on Darwin 10.rebuild-linux: 0 This PR does not cause any packages to rebuild on Linux labels Jul 30, 2021
@samueldr samueldr merged commit ca5d520 into NixOS:master Jul 30, 2021
@lopsided98 lopsided98 deleted the armv7l-disable-lpae branch July 30, 2021 19:41
@github-actions github-actions bot mentioned this pull request Jul 30, 2021
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Successfully created backport PR #132162 for release-21.05.

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@samueldr samueldr samueldr approved these changes

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6.topic: kernel The Linux kernel 10.rebuild-darwin: 0 This PR does not cause any packages to rebuild on Darwin 10.rebuild-linux: 0 This PR does not cause any packages to rebuild on Linux
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@lopsided98 @samueldr