[v2,0/5] cpu/speculation: Add 'mitigations=' cmdline option

v2:
- docs improvements: [Randy, Michael]
- Rename to "mitigations=" [Michael]
- Add cpu_mitigations_off() function wrapper [Michael]
- x86: Simplify logic [Boris]
- powerpc: Fix no_rfi_flush checking bug (use '&&' instead of '||')
- arm64: Rebase onto Jeremy Linton's v7 patches [Will]
- arm64: "kpti command line option" [Steve P]
- arm64: Add nospectre_v2 support

-----------

Keeping track of the number of mitigations for all the CPU speculation
bugs has become overwhelming for many users.  It's getting more and more
complicated to decide which mitigations are needed for a given
architecture.  Complicating matters is the fact that each arch tends to
have its own custom way to mitigate the same vulnerability.

Most users fall into a few basic categories:

a) they want all mitigations off;

b) they want all reasonable mitigations on, with SMT enabled even if
   it's vulnerable; or

c) they want all reasonable mitigations on, with SMT disabled if
   vulnerable.

Define a set of curated, arch-independent options, each of which is an
aggregation of existing options:

- mitigations=off: Disable all mitigations.

- mitigations=auto: [default] Enable all the default mitigations, but
  leave SMT enabled, even if it's vulnerable.

- mitigations=auto,nosmt: Enable all the default mitigations, disabling
  SMT if needed by a mitigation.

Josh Poimboeuf (5):
  cpu/speculation: Add 'mitigations=' cmdline option
  x86/speculation: Support 'mitigations=' cmdline option
  powerpc/speculation: Support 'mitigations=' cmdline option
  s390/speculation: Support 'mitigations=' cmdline option
  arm64/speculation: Support 'mitigations=' cmdline option

 .../admin-guide/kernel-parameters.txt         | 34 +++++++++++++++++++
 arch/arm64/kernel/cpu_errata.c                |  6 +++-
 arch/arm64/kernel/cpufeature.c                |  8 ++++-
 arch/powerpc/kernel/security.c                |  6 ++--
 arch/powerpc/kernel/setup_64.c                |  2 +-
 arch/s390/kernel/nospec-branch.c              |  3 +-
 arch/x86/kernel/cpu/bugs.c                    | 11 ++++--
 arch/x86/mm/pti.c                             |  4 ++-
 include/linux/cpu.h                           | 24 +++++++++++++
 kernel/cpu.c                                  | 15 ++++++++
 10 files changed, 103 insertions(+), 10 deletions(-)

On Fri, 12 Apr 2019, Josh Poimboeuf wrote:

> v2:
> - docs improvements: [Randy, Michael]
> - Rename to "mitigations=" [Michael]
> - Add cpu_mitigations_off() function wrapper [Michael]
> - x86: Simplify logic [Boris]
> - powerpc: Fix no_rfi_flush checking bug (use '&&' instead of '||')
> - arm64: Rebase onto Jeremy Linton's v7 patches [Will]
> - arm64: "kpti command line option" [Steve P]
> - arm64: Add nospectre_v2 support
> 
> -----------
> 
> Keeping track of the number of mitigations for all the CPU speculation
> bugs has become overwhelming for many users.  It's getting more and more
> complicated to decide which mitigations are needed for a given
> architecture.  Complicating matters is the fact that each arch tends to
> have its own custom way to mitigate the same vulnerability.
> 
> Most users fall into a few basic categories:
> 
> a) they want all mitigations off;
> 
> b) they want all reasonable mitigations on, with SMT enabled even if
>    it's vulnerable; or
> 
> c) they want all reasonable mitigations on, with SMT disabled if
>    vulnerable.
> 
> Define a set of curated, arch-independent options, each of which is an
> aggregation of existing options:
> 
> - mitigations=off: Disable all mitigations.
> 
> - mitigations=auto: [default] Enable all the default mitigations, but
>   leave SMT enabled, even if it's vulnerable.
> 
> - mitigations=auto,nosmt: Enable all the default mitigations, disabling
>   SMT if needed by a mitigation.
> 
> Josh Poimboeuf (5):
>   cpu/speculation: Add 'mitigations=' cmdline option
>   x86/speculation: Support 'mitigations=' cmdline option
>   powerpc/speculation: Support 'mitigations=' cmdline option
>   s390/speculation: Support 'mitigations=' cmdline option
>   arm64/speculation: Support 'mitigations=' cmdline option

Tested-by: Jiri Kosina <jkosina@suse.cz> (on x86)
Reviewed-by: Jiri Kosina <jkosina@suse.cz>

Thanks,