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SubjectRe: [PATCH v2 05/17] arm64: Add 'ssbd' command-line option
On 05/29/2018 08:11 AM, Marc Zyngier wrote:

> + ssbd= [ARM64,HW]
> + Speculative Store Bypass Disable control
> +
> + On CPUs that are vulnerable to the Speculative
> + Store Bypass vulnerability and offer a
> + firmware based mitigation, this parameter
> + indicates how the mitigation should be used:
> +
> + force-on: Unconditionally enable mitigation for
> + for both kernel and userspace
> + force-off: Unconditionally disable mitigation for
> + for both kernel and userspace
> + kernel: Always enable mitigation in the
> + kernel, and offer a prctl interface
> + to allow userspace to register its
> + interest in being mitigated too.

This should be "spec_store_bypass_disable" and it should have the same
parameters as on x86: "on", "off", "auto". Why not just add "kernel"?
(we had a "kernel" early on for x86 as well, and it might still end up
coming back anyway). If there's a /compelling/ reason to have the Arm
parameter differ, then it should still recognize the x86 parameter,
similarly to how POWER also does that for cross-arch consistency.

We'll add the x86 parameter way of doing it to RHEL anyway.

Jon.

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