From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3BC42C742C2 for ; Fri, 12 Jul 2019 13:54:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1F3252080A for ; Fri, 12 Jul 2019 13:54:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727888AbfGLNy2 (ORCPT ); Fri, 12 Jul 2019 09:54:28 -0400 Received: from mga17.intel.com ([192.55.52.151]:38140 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726977AbfGLNyZ (ORCPT ); Fri, 12 Jul 2019 09:54:25 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Jul 2019 06:54:24 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,482,1557212400"; d="scan'208";a="166683884" Received: from smatond1-mobl1.amr.corp.intel.com (HELO [10.252.143.186]) ([10.252.143.186]) by fmsmga008.fm.intel.com with ESMTP; 12 Jul 2019 06:54:22 -0700 Subject: Re: [RFC v2 00/27] Kernel Address Space Isolation To: Peter Zijlstra , Alexandre Chartre Cc: Thomas Gleixner , pbonzini@redhat.com, rkrcmar@redhat.com, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, dave.hansen@linux.intel.com, luto@kernel.org, kvm@vger.kernel.org, x86@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, konrad.wilk@oracle.com, jan.setjeeilers@oracle.com, liran.alon@oracle.com, jwadams@google.com, graf@amazon.de, rppt@linux.vnet.ibm.com, Paul Turner References: <1562855138-19507-1-git-send-email-alexandre.chartre@oracle.com> <5cab2a0e-1034-8748-fcbe-a17cf4fa2cd4@intel.com> <61d5851e-a8bf-e25c-e673-b71c8b83042c@oracle.com> <20190712125059.GP3419@hirez.programming.kicks-ass.net> From: Dave Hansen Openpgp: preference=signencrypt Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <20190712125059.GP3419@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/12/19 5:50 AM, Peter Zijlstra wrote: > PTI is not mapping kernel space to avoid speculation crap (meltdown). > ASI is not mapping part of kernel space to avoid (different) speculation crap (MDS). > > See how very similar they are? That's an interesting point. I'd add that PTI maps a part of kernel space that partially overlaps with what ASI wants. > But looking at it that way, it makes no sense to retain 3 address > spaces, namely: > > user / kernel exposed / kernel private. > > Specifically, it makes no sense to expose part of the kernel through MDS > but not through Meltdown. Therefore we can merge the user and kernel > exposed address spaces. > > And then we've fully replaced PTI. So, in one address space (PTI/user or ASI), we say, "screw it" and all the data mapped is exposed to speculation attacks. We have to be very careful about what we map and expose here. The other (full kernel) address space we are more careful about what we *do* instead of what we map. We map everything but have to add mitigations to ensure that we don't leak anything back to the exposed address space. So, maybe we're not replacing PTI as much as we're growing PTI so that we can run more kernel code with the (now inappropriately named) user page tables.