Re: [PATCH 0/2] x86/split_lock: Fix and cleanup of cpu_model_supports_sld

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 12/18/2025 4:00 PM, Xiaoyao Li wrote:
> While considering Kiryl's suggestion[1], I'm wondering why we have
> cpu_model_supports_sld defined, which seems like it could be replaced by
> X86_FEATURE_SPLIT_LOCK_DETECT.
> 
> Tracing through the history, I find that X86_FEATURE_SPLIT_LOCK_DETECT
> originally indicated whether the kernel enabled the split lock detection
> feature, rather than enumerating hardware support for the feature, at the
> time when cpu_model_supports_sld was introduced.
> 
> Now, the semantics of X86_FEATURE_SPLIT_LOCK_DETECT have changed and
> it enuemrates the hardware support for the feature. Therefore, patch 2
> replaces cpu_model_supports_sld with X86_FEATURE_SPLIT_LOCK_DETECT.
> 
> Patch 1 fixes a potential issue where MSR_TEST_CTRL can be written when
> the split lock detection feature is not available, which can cause bizarre
> behavior.

Ping on this series.

(It applies cleanly on v7.0-rc2)

> [1] https://lore.kernel.org/all/lvobu4gpfsjg63syubgy2jwcja72folflrst7bu2eqv6rhaqre@ttbkykphu32f/
> 
> Xiaoyao Li (2):
>    x86/split_lock: Fix handling in split_lock_init()
>    x86/split_lock: Drop cpu_model_supports_sld
> 
>   arch/x86/kernel/cpu/bus_lock.c | 14 ++++----------
>   1 file changed, 4 insertions(+), 10 deletions(-)
>