On 01/18/2018 08:37 AM, Josh Poimboeuf wrote: >> >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -3932,6 +3932,7 @@ >> retpoline - replace indirect branches >> retpoline,generic - google's original retpoline >> retpoline,amd - AMD-specific minimal thunk >> + ibrs - Intel: Indirect Branch Restricted >> Speculation > Are there plans to add spectre_v2=ibrs_always to prevent SMT-based > attacks?
What does "ibrs_always" mean to you? There is a second bit in the MSR (STIBP) that is intended to keep hyperthreads from influencing each-other. That is behavior is implicit when IBRS is enabled. I think ibrs_always *should* probably be kept to refer to the future CPUs that can safely leave IBRS enabled all the time.
