linux-kernel - Re: [PATCH 2/2] x86/speculation: Provide application property based STIBP protection

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Date:   Tue, 2 Oct 2018 11:41:28 -0400
From:   Jon Masters <jcm@...hat.com>
To:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Jiri Kosina <jikos@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Tom Lendacky <thomas.lendacky@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 2/2] x86/speculation: Provide application property based
 STIBP protection

On 9/19/18 5:35 PM, Tim Chen wrote:
> This patch provides an application property based spectre_v2
> protection with STIBP against attack from another app from
> a sibling hyper-thread.  For security sensitive non-dumpable
> app, STIBP will be turned on before switching to it for Intel
> processors vulnerable to spectre_v2.

A general comment. I think in practice this will be similar to the
speculative store buffer bypass (aka "variant 4") issue in terms of
opt-in mitigation. Many users won't want to take the performance hit of
having STIBP by default for peer threads. We should make sure that we
don't force users into a mitigation but retain an option. Whether it's
default-on or not can be debated, though I think the vendors lean toward
having default-off with an opt-in, and customers will probably agree. So
anyway, I encourage a pragmatic approach similar to that for SSBD.

Jon.

-- 
Computer Architect | Sent with my Fedora powered laptop