[PATCH 0/2] cpu: Fix default mitigation behavior

[Sean Christopherson]

This is effectively v2 of a previous series[*] that was intended to be
x86-only, but accidentally disabled CPU mitigations by default for every
other architectures.  Unfortunately, the buggy code has already made it's
way to Linus' tree.

Patch 1 fixes that goof by adding a generic Kconfig to control the
default behavior.

Patch 2 disallows retroactively enabling mitigations via command line if
the kernel was built with CPU_MITIGATIONS=n, i.e. with
SPECULATION_MITIGATIONS=n on x86, as it's infeasible for the kernel to
provide sane, predictable behavior for this scenario.

[*] https://lore.kernel.org/all/20240409175108.1512861-1-seanjc@xxxxxxxxxx

Sean Christopherson (2):
  cpu: Re-enable CPU mitigations by default for !X86 architectures
  cpu: Ignore "mitigations" kernel parameter if CPU_MITIGATIONS=n

 Documentation/admin-guide/kernel-parameters.txt |  3 +++
 arch/x86/Kconfig                                | 11 ++++++++---
 drivers/base/Kconfig                            |  3 +++
 kernel/cpu.c                                    |  6 ++++--
 4 files changed, 18 insertions(+), 5 deletions(-)


base-commit: 96fca68c4fbf77a8185eb10f7557e23352732ea2
-- 
2.44.0.683.g7961c838ac-goog