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From:   Jon Masters <jcm@redhat.com>
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Subject: Re: [PATCH 2/2] x86/speculation: Provide application property based STIBP protection
Message-Id: <ED92A4DA-E9A3-4AED-90B4-4A912864EACE@redhat.com>
Date:   Tue, 2 Oct 2018 11:44:55 -0400 (EDT)
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> <nycvar.YFH.7.76.1810021742540.14430@cbobk.fhfr.pm>
To:     Jiri Kosina <jikos@kernel.org>
In-Reply-To: <nycvar.YFH.7.76.1810021742540.14430@cbobk.fhfr.pm>
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
Thread-Topic: x86/speculation: Provide application property based STIBP protection
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Quick reply: I agree, I'm just supporting this :)

-- 
Computer Architect


> On Oct 2, 2018, at 11:43, Jiri Kosina <jikos@kernel.org> wrote:
> 
> 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
>