Messages in this thread | | | From | "Luck, Tony" <> | Subject | RE: [PATCH v12] x86/split_lock: Enable split lock detection by kernel | Date | Wed, 22 Jan 2020 23:24:34 +0000 |
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>> +static enum split_lock_detect_state sld_state = sld_warn; >> + > > This sets sld_state to sld_warn even on CPUs that don't support > split-lock detection. split_lock_init will then try to read/write the > MSR to turn it on. Would it be better to initialize it to sld_off and > set it to sld_warn in split_lock_setup instead, which is only called if > the CPU supports the feature?
I've lost some bits of this patch series somewhere along the way :-( There was once code to decide whether the feature was supported (either with x86_match_cpu() for a couple of models, or using the architectural test based on some MSR bits. I need to dig that out and put it back in. Then stuff can check X86_FEATURE_SPLIT_LOCK before wandering into code that messes with MSRs
>> + if (!split_lock_detect_enabled()) >> + return; > > This misses one comment from Sean [1] that this check should be dropped, > otherwise user-space alignment check via EFLAGS.AC will get ignored when > split lock detection is disabled.
Ah yes. Good catch. Will fix.
Thanks for the review.
-Tony
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