Josh Poimboeuf <jpoim...@redhat.com> writes:
> Configure powerpc CPU runtime speculation bug mitigations in accordance
> with the 'cpu_spec_mitigations=' cmdline options.  This affects
> Meltdown, Spectre v1, Spectre v2, and Speculative Store Bypass.
>
> The default behavior is unchanged.
>
> Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt | 9 +++++----
>  arch/powerpc/kernel/security.c                  | 6 +++---
>  arch/powerpc/kernel/setup_64.c                  | 2 +-
>  3 files changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt 
> b/Documentation/admin-guide/kernel-parameters.txt
> index 29dc03971630..0e8eae1e8a25 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2552,10 +2552,11 @@
>  
>                       off
>                               Disable all speculative CPU mitigations.
> -                             Equivalent to: nopti [x86]
> +                             Equivalent to: nopti [x86, powerpc]
> +                                            nospectre_v1 [powerpc]
>                                              nospectre_v2 [x86]

Not sure if you meant to omit powerpc from nospectre_v2?

You have patched it in the code below.

>                                              spectre_v2_user=off [x86]
> -                                            spec_store_bypass_disable=off 
> [x86]
> +                                            spec_store_bypass_disable=off 
> [x86, powerpc]
>                                              l1tf=off [x86]
>  
>                       auto (default)
> @@ -2568,7 +2569,7 @@
>                               Equivalent to: pti=auto [x86]
>                                              spectre_v2=auto [x86]
>                                              spectre_v2_user=auto [x86]
> -                                            spec_store_bypass_disable=auto 
> [x86]
> +                                            spec_store_bypass_disable=auto 
> [x86, powerpc]
>                                              l1tf=flush [x86]
>  
>                       auto,nosmt
> @@ -2579,7 +2580,7 @@
>                               Equivalent to: pti=auto [x86]
>                                              spectre_v2=auto [x86]
>                                              spectre_v2_user=auto [x86]
> -                                            spec_store_bypass_disable=auto 
> [x86]
> +                                            spec_store_bypass_disable=auto 
> [x86, powerpc]
>                                              l1tf=flush,nosmt [x86]
>  
>       mminit_loglevel=
> diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
> index b33bafb8fcea..5aed4ad729ba 100644
> --- a/arch/powerpc/kernel/security.c
> +++ b/arch/powerpc/kernel/security.c
> @@ -57,7 +57,7 @@ void setup_barrier_nospec(void)
>       enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
>                security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR);
>  
> -     if (!no_nospec)
> +     if (!no_nospec && cpu_spec_mitigations != CPU_SPEC_MITIGATIONS_OFF)
>               enable_barrier_nospec(enable);

Adding a wrapper func that checks for CPU_SPEC_MITIGATIONS_OFF would
make these a little less verbose, eg:

        if (!no_nospec && !cpu_spec_mitigations_off())
                enable_barrier_nospec(enable);

But that's a nitpick.

> @@ -116,7 +116,7 @@ static int __init handle_nospectre_v2(char *p)
>  early_param("nospectre_v2", handle_nospectre_v2);
>  void setup_spectre_v2(void)
>  {
> -     if (no_spectrev2)
> +     if (no_spectrev2 || cpu_spec_mitigations == CPU_SPEC_MITIGATIONS_OFF)
>               do_btb_flush_fixups();
>       else
>               btb_flush_enabled = true;
> @@ -300,7 +300,7 @@ void setup_stf_barrier(void)
>  
>       stf_enabled_flush_types = type;
>  
> -     if (!no_stf_barrier)
> +     if (!no_stf_barrier && cpu_spec_mitigations != CPU_SPEC_MITIGATIONS_OFF)
>               stf_barrier_enable(enable);
>  }
>  
> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> index ba404dd9ce1d..d9d796a66a79 100644
> --- a/arch/powerpc/kernel/setup_64.c
> +++ b/arch/powerpc/kernel/setup_64.c
> @@ -932,7 +932,7 @@ void setup_rfi_flush(enum l1d_flush_type types, bool 
> enable)
>  
>       enabled_flush_types = types;
>  
> -     if (!no_rfi_flush)
> +     if (!no_rfi_flush || cpu_spec_mitigations != CPU_SPEC_MITIGATIONS_OFF)
>               rfi_flush_enable(enable);
>  }

LGTM.

Acked-by: Michael Ellerman <m...@ellerman.id.au> (powerpc)

cheers

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