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SubjectRe: [PATCH 23/35] x86/speculation: Add basic speculation control code
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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.

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