linux-kernel - Re: [PATCH 2/3] x86/speculation: Support Automatic IBRS

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Message-ID: <Y2ZEinL+wlIX+1Sn@hirez.programming.kicks-ass.net>
Date:   Sat, 5 Nov 2022 12:10:02 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Kim Phillips <kim.phillips@....com>, x86@...nel.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Juergen Gross <jgross@...e.com>,
        Tony Luck <tony.luck@...el.com>,
        Babu Moger <Babu.Moger@....com>,
        Tom Lendacky <thomas.lendacky@....com>, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] x86/speculation: Support Automatic IBRS

On Fri, Nov 04, 2022 at 10:52:13PM +0100, Borislav Petkov wrote:
> On Fri, Nov 04, 2022 at 04:36:50PM -0500, Kim Phillips wrote:
> >  - Allow for spectre_v2=autoibrs in the kernel command line,
> >    reverting to auto-selection if the feature isn't available.
> 
> Why?
> 
> What the whole logic here should do is enable autoibrs when detected
> automatically, without the need for the user to even select it as it is
> the superior mitigation.

Well; perhaps the whole autoibrs thing should be mapped to the existing
eIBRS options. AFAICT this is the same thing under a new name, no need
to invent yet more options. bugs.c is quite insane enough already.