x86/cpu: Fix SPECULATIVE_MITIGATION=n kernels

[PATCH 0/3] x86/cpu: Fix SPECULATIVE_MITIGATION=n kernels

Posted by Sean Christopherson 1 year, 10 months ago

Fix the handling of SPECULATION_MITIGATIONS=n so that it actually does
what it says it does: disable any and all mitigations.

And because I don't see a way to provide sane behavior for overriding
SPECULATION_MITIGATIONS=n at runtime, explicitly disallow doing so via
the "mitigations" kernel parameter, e.g. so that the user at least knows
that their system is still likely vulnerable to a variety of issues.

Sean Christopherson (3):
  x86/cpu: Actually turn off mitigations by default for
    SPECULATION_MITIGATIONS=n
  x86/cpu: Disable BHI mitigation by default when
    SPECULATION_MITIGATIONS=n
  x86/cpu: Ignore "mitigations" kernel parameter if
    SPECULATION_MITIGATIONS=n

 Documentation/admin-guide/kernel-parameters.txt |  3 +++
 arch/x86/Kconfig                                | 10 +++++++---
 arch/x86/kernel/cpu/bugs.c                      |  6 +++---
 kernel/cpu.c                                    |  5 ++++-
 4 files changed, 17 insertions(+), 7 deletions(-)


base-commit: 2c71fdf02a95b3dd425b42f28fd47fb2b1d22702
-- 
2.44.0.478.gd926399ef9-goog

Re: [PATCH 0/3] x86/cpu: Fix SPECULATIVE_MITIGATION=n kernels

Posted by Daniel Sneddon 1 year, 10 months ago

On 4/9/24 10:51, Sean Christopherson wrote:
> Fix the handling of SPECULATION_MITIGATIONS=n so that it actually does
> what it says it does: disable any and all mitigations.
> 
> And because I don't see a way to provide sane behavior for overriding
> SPECULATION_MITIGATIONS=n at runtime, explicitly disallow doing so via
> the "mitigations" kernel parameter, e.g. so that the user at least knows
> that their system is still likely vulnerable to a variety of issues.
> 
> Sean Christopherson (3):
>   x86/cpu: Actually turn off mitigations by default for
>     SPECULATION_MITIGATIONS=n
>   x86/cpu: Disable BHI mitigation by default when
>     SPECULATION_MITIGATIONS=n
>   x86/cpu: Ignore "mitigations" kernel parameter if
>     SPECULATION_MITIGATIONS=n
> 
>  Documentation/admin-guide/kernel-parameters.txt |  3 +++
>  arch/x86/Kconfig                                | 10 +++++++---
>  arch/x86/kernel/cpu/bugs.c                      |  6 +++---
>  kernel/cpu.c                                    |  5 ++++-
>  4 files changed, 17 insertions(+), 7 deletions(-)
> 
> 
> base-commit: 2c71fdf02a95b3dd425b42f28fd47fb2b1d22702

Reviewed-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>