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Date:   Tue, 2 Oct 2018 17:43:16 +0200 (CEST)
From:   Jiri Kosina <jikos@kernel.org>
To:     Jon Masters <jcm@redhat.com>
cc:     Tim Chen <tim.c.chen@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        David Woodhouse <dwmw@amazon.co.uk>,
        Andi Kleen <ak@linux.intel.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Casey Schaufler <casey.schaufler@intel.com>,
        Asit Mallick <asit.k.mallick@intel.com>,
        Arjan van de Ven <arjan@linux.intel.com>,
        linux-kernel@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH 2/2] x86/speculation: Provide application property based
 STIBP protection
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References: <cover.1537392876.git.tim.c.chen@linux.intel.com> <0c55c162a077aadbfd57878e2694e35292c1a29c.1537392876.git.tim.c.chen@linux.intel.com> <1a501628-a232-a126-166e-814c26243f2d@redhat.com>
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On Tue, 2 Oct 2018, Jon Masters 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.

Which is what Tim's patchset is implementing on top.

Thanks,

-- 
Jiri Kosina
SUSE Labs