Re: [PATCH v12 05/12] x86/vmscape: Move mitigation selection to a switch()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The use of a `default:` label in the `switch` statement defeats the compiler's ability to ensure all mitigation modes are explicitly handled.
--

commit 5e3a6ba10ff7b033ea17daee7432bcf9168f3b13
Author: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>

x86/vmscape: Move mitigation selection to a switch()

This commit refactors the vmscape mitigation selection logic to use a switch
statement. The stated goal is to explicitly handle all mitigation modes and
group the logic for each mode together in preparation for future additions.

> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
[ ... ]
> @@ -3088,17 +3088,33 @@ early_param("vmscape", vmscape_parse_cmdline);
>  
>  static void __init vmscape_select_mitigation(void)
>  {
[ ... ]
> +	switch (vmscape_mitigation) {
> +	case VMSCAPE_MITIGATION_NONE:
> +		break;
> +
> +	case VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER:
> +		if (!boot_cpu_has(X86_FEATURE_IBPB))
> +			vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
> +		break;
> +
> +	case VMSCAPE_MITIGATION_AUTO:
> +		if (boot_cpu_has(X86_FEATURE_IBPB))
> +			vmscape_mitigation = VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER;
> +		else
> +			vmscape_mitigation = VMSCAPE_MITIGATION_NONE;
> +		break;
> +
> +	default:
> +		break;

[Severity: Medium]
Does including a default case here defeat the stated goal of the patch?

The commit message notes this refactor "ensures that all mitigation modes are
explicitly handled". However, including a default block suppresses compiler
warnings about unhandled enum values.

If future mitigation modes are added to the enum but forgotten in this switch,
they will silently fall through to the default case rather than generating a
compile-time warning.

>  	}
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260622-vmscape-bhb-v12-0-76cbda0ae3e5@linux.intel.com?part=5