Re: [PATCH v2] x86/split_lock: Handle unexpected split lock as fatal

[Dave Hansen <dave.hansen@intel.com>]

On 1/7/26 05:49, Xiaoyao Li wrote:
> +	/*
> +	 * If #AC occurs on split lock without X86_FEATURE_SPLIT_LOCK_DETECT
> +	 * the kernel cannot handle it by disabling the detection. Treat it as
> +	 * fatal regardless of the sld_state.
> +	 */
> +	if (!cpu_feature_enabled(X86_FEATURE_SPLIT_LOCK_DETECT))
> +		return true;

If #AC occurs on split lock without X86_FEATURE_SPLIT_LOCK_DETECT, that
sounds more like a naughty hypervisor or buggy CPU that deserves a
BUG_ON() rather than a situation where the kernel wants to move merrily
along.

This also needs an explanation in the changelog about _why_
X86_FEATURE_SPLIT_LOCK_DETECT isn't set and can't be set. It needs to
explain why enumeration is not present *AND* is impossible to add.