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Subject: Re: [PATCH] x86/speculation: Add document to describe Spectre and its
 mitigations
To:     Jiri Kosina <jikos@kernel.org>, Pavel Machek <pavel@ucw.cz>
Cc:     Tim Chen <tim.c.chen@linux.intel.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        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>,
        Asit Mallick <asit.k.mallick@intel.com>,
        Jon Masters <jcm@redhat.com>,
        Waiman Long <longman9394@gmail.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Borislav Petkov <bp@alien8.de>, linux-kernel@vger.kernel.org,
        x86@kernel.org, stable@vger.kernel.org
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 <20190113231001.GB18710@amd>
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 <20190114120157.GB21544@amd>
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 <20190114130153.GC21544@amd>
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From:   Arjan van de Ven <arjan@linux.intel.com>
Message-ID: <5907b2bc-8498-2f28-eb90-13627d492496@linux.intel.com>
Date:   Mon, 14 Jan 2019 06:39:33 -0800
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On 1/14/2019 5:06 AM, Jiri Kosina wrote:
> On Mon, 14 Jan 2019, Pavel Machek wrote:
> 
>> Frankly I'd not call it Meltdown, as it works only on data in the cache,
>> so the defense is completely different. Seems more like a l1tf
>> :-).
> 
> Meltdown on x86 also seems to work only for data in L1D, but the pipeline
> could be constructed in a way that data are actually fetched into L1D
> before speculation gives up, which is not the case on ppc (speculation
> aborts on L2->L1 propagation IIRC). That's why flushing L1D on ppc is
> sufficient, but on x86 it's not.

assuming L1D is not shared between SMT threads obviously :)

>