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

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

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.

[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(-)

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2.43.0