Re: [PATCH v2 5/5] arm64/speculation: Support 'mitigations=' cmdline option

Randy Dunlap
2019-04-12T23:34:47Z

On 4/12/19 1:39 PM, Josh Poimboeuf wrote:
> Configure arm64 runtime CPU speculation bug mitigations in accordance
> with the 'mitigations=' cmdline option. This affects Meltdown, Spectre
> v2, and Speculative Store Bypass.
>
> The default behavior is unchanged.
>
> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> ---
> NOTE: This is based on top of Jeremy Linton's patches:
> https://lkml.kernel.org/r/20190410231237.52506-1-jeremy.linton@arm.com
>
> Documentation/admin-guide/kernel-parameters.txt | 8 +++++---
> arch/arm64/kernel/cpu_errata.c | 6 +++++-
> arch/arm64/kernel/cpufeature.c | 8 +++++++-
> 3 files changed, 17 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index e84a01d90e92..79bfc755defe 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2545,8 +2545,8 @@
> http://repo.or.cz/w/linux-2.6/mini2440.git
>
> mitigations=
> - [X86,PPC,S390] Control optional mitigations for CPU
> - vulnerabilities. This is a set of curated,
> + [X86,PPC,S390,ARM64] Control optional mitigations for
> + CPU vulnerabilities. This is a set of curated,
> arch-independent options, each of which is an
> aggregation of existing arch-specific options.
>
> @@ -2555,11 +2555,13 @@
> improves system performance, but it may also
> expose users to several CPU vulnerabilities.
> Equivalent to: nopti [X86,PPC]
> + kpti=0 [ARM64]
> nospectre_v1 [PPC]
> nobp=0 [S390]
> - nospectre_v2 [X86,PPC,S390]
> + nospectre_v2 [X86,PPC,S390,ARM64]
> spectre_v2_user=off [X86]
> spec_store_bypass_disable=off [X86,PPC]
> + ssbd=force-off [ARM64]
> l1tf=off [X86]
>
> auto (default)

Hi,
Do we need to add "ARM64" to Documentation/admin-guide/kernel-parameters.rst?

--
~Randy