Re: [PATCH v2] x86/speculation: Add support for STIBP always-on preferred mode

Lendacky, Thomas
2018-12-12T14:04:41Z

On 12/12/2018 03:59 AM, Borislav Petkov wrote:
> On Tue, Dec 11, 2018 at 07:37:26PM -0800, Thomas Gleixner wrote:
>> Hmmm. I've not seen the V1 of this (it's not in my inbox) but the v1->v2
>> changes contain:
>
> You're on CC:
>
> https://lkml.kernel.org/r/20181211190959.28321.56433.stgit@tlendack-t1.amdoffice.net
>
>>
>>>> - Removed explicit SPECTRE_V2_USER_STRICT_PREFERRED mode
>>
>> Now I really have to ask why?
>>
>> Neither the extra variable nor the cpu feature check are pretty. An
>> explicit mode is way better in terms of code clarity and you get the proper
>> printout via spectre_v2_user_strings.
>
> Actually, now that I've slept on it, I think we should do this just
> like X86_FEATURE_IBRS_ENHANCED - as a modifier for SPECTRE_V2_CMD_AUTO
> or _FORCE options.
>
> And that has its own mode SPECTRE_V2_IBRS_ENHANCED.
>
> Makes sense?

Not sure I completely follow. Are you saying to do what I did in my
first patch or something different from that yet?

Thanks,
Tom

>