linux-kernel - Re: [PATCH v2 1/2] x86/speculation: Allow enabling STIBP with legacy IBRS

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Message-ID: <Y/YLYbr5CV2Vtxph@zn.tnic>
Date:   Wed, 22 Feb 2023 13:32:33 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     KP Singh <kpsingh@...nel.org>
Cc:     Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        linux-kernel@...r.kernel.org, pjt@...gle.com, evn@...gle.com,
        jpoimboe@...nel.org, tglx@...utronix.de, x86@...nel.org,
        hpa@...or.com, peterz@...radead.org, kim.phillips@....com,
        alexandre.chartre@...cle.com, daniel.sneddon@...ux.intel.com,
        corbet@....net, bp@...e.de, linyujun809@...wei.com,
        jmattson@...gle.com,
        José Oliveira <joseloliveira11@...il.com>,
        Rodrigo Branco <rodrigo@...nelhacking.com>,
        Alexandra Sandulescu <aesa@...gle.com>, stable@...r.kernel.org
Subject: Re: [PATCH v2 1/2] x86/speculation: Allow enabling STIBP with legacy
 IBRS

On Tue, Feb 21, 2023 at 09:49:57PM -0800, KP Singh wrote:
> That is a bit more complicated as, for now, the user is not really
> exposed to STIBP explicitly yet.

Remember that we're exposing the normal user to a gazillion switches
already. And not every user has done a PhD in hw vulns like we were
forced to in the last, at least 5, years.

So whatever you do, you should try to make it work automatic - if
possible - and DTRT - i.e., sane defaults.

Every new functionality added to that madness needs a proper
justification.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette