Messages in this thread | | | From | Andy Lutomirski <> | Date | Sat, 9 May 2020 22:14:02 -0700 | Subject | Re: [PATCH v9 3/8] x86/split_lock: Introduce flag X86_FEATURE_SLD_FATAL and drop sld_state |
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On Fri, May 8, 2020 at 8:03 PM Xiaoyao Li <xiaoyao.li@intel.com> wrote: > > Introduce a synthetic feature flag X86_FEATURE_SLD_FATAL, which means > kernel is in sld_fatal mode if set. > > Now sld_state is not needed any more that the state of SLD can be > inferred from X86_FEATURE_SPLIT_LOCK_DETECT and X86_FEATURE_SLD_FATAL.
Is it too much to ask for Intel to actually allocate and define a CPUID bit that means "this CPU *always* sends #AC on a split lock"? This would be a pure documentation change, but it would make this architectural rather than something that each hypervisor needs to hack up.
Meanwhile, I don't see why adding a cpufeature flag is worthwhile to avoid a less bizarre global variable. There's no performance issue here, and the old code looked a lot more comprehensible than the new code.
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