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

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Date:   Wed, 12 Dec 2018 15:01:50 +0000
From:   "Lendacky, Thomas" <Thomas.Lendacky@....com>
To:     Boris Petkov <bp@...en8.de>, Thomas Gleixner <tglx@...utronix.de>
CC:     "x86@...nel.org" <x86@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Jiri Kosina <jkosina@...e.cz>, Ingo Molnar <mingo@...hat.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        David Woodhouse <dwmw@...zon.co.uk>
Subject: Re: [PATCH v2] x86/speculation: Add support for STIBP always-on
 preferred mode

On 12/12/2018 08:32 AM, Boris Petkov wrote:
> On December 12, 2018 3:04:35 PM GMT+01:00, "Lendacky, Thomas" <Thomas.Lendacky@....com> wrote:
>> Not sure I completely follow. Are you saying to do what I did in my
>> first patch or something different from that yet?
> 
> I'm saying that STIBP_ALWAYS_ON should be implemented the same way like IBRS_ENHANCED is and there's no need for a static bool. AFAICT.
> 
> Or am I missing something? 

Ok, I think you're saying to do what my first patch did or something very
close to that. Which is to just set always-on mode if STIBP protection is
requested and the STIBP_ALWAYS_ON CPUID bit is set (even if the equivalent
"=on" is supplied on the command line?). That would mean having the new
mode and new string(s).

If that's not what you're saying, then maybe I just need more coffee this
morning :)

Thanks,
Tom

>