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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 8BC1FC43460 for ; Tue, 6 Apr 2021 14:33:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0E7E9613D4 for ; Tue, 6 Apr 2021 14:33:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0E7E9613D4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 831986B0085; Tue, 6 Apr 2021 10:33:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7E0BA6B0087; Tue, 6 Apr 2021 10:33:08 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 633156B0088; Tue, 6 Apr 2021 10:33:08 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0246.hostedemail.com [216.40.44.246]) by kanga.kvack.org (Postfix) with ESMTP id 459E06B0085 for ; Tue, 6 Apr 2021 10:33:08 -0400 (EDT) Received: from smtpin36.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 082141DFF for ; Tue, 6 Apr 2021 14:33:08 +0000 (UTC) X-FDA: 78002184456.36.3E1AC6D Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by imf21.hostedemail.com (Postfix) with ESMTP id 95A83E000108 for ; Tue, 6 Apr 2021 14:33:05 +0000 (UTC) IronPort-SDR: tyQD4vVHyrYHyGzZndet65yNUcDN+6ZXak+DUyKCvupAU7g7SapDl/6/L8zlmgB49LjASy/t/4 uYezJ5oCyEAg== X-IronPort-AV: E=McAfee;i="6000,8403,9946"; a="278337965" X-IronPort-AV: E=Sophos;i="5.81,309,1610438400"; d="scan'208";a="278337965" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Apr 2021 07:33:04 -0700 IronPort-SDR: YL1dNphUsw0l80VGVme5Zr/g6N1Prqg0n5R4QnNdQniE/FVpbXDIbH1niH7yIKrcN2Qjelw17o F3+DzoXsADng== X-IronPort-AV: E=Sophos;i="5.81,309,1610438400"; d="scan'208";a="418376975" Received: from etbenite-mobl1.amr.corp.intel.com (HELO [10.212.54.229]) ([10.212.54.229]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Apr 2021 07:33:02 -0700 Subject: Re: [RFCv1 7/7] KVM: unmap guest memory using poisoned pages To: David Hildenbrand , "Kirill A. Shutemov" , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Sean Christopherson , Jim Mattson Cc: David Rientjes , "Edgecombe, Rick P" , "Kleen, Andi" , "Yamahata, Isaku" , x86@kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A. Shutemov" References: <20210402152645.26680-1-kirill.shutemov@linux.intel.com> <20210402152645.26680-8-kirill.shutemov@linux.intel.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; keydata= xsFNBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABzShEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gPGRhdmVAc3I3MS5uZXQ+wsF7BBMBAgAlAhsDBgsJCAcDAgYVCAIJ CgsEFgIDAQIeAQIXgAUCTo3k0QIZAQAKCRBoNZUwcMmSsMO2D/421Xg8pimb9mPzM5N7khT0 2MCnaGssU1T59YPE25kYdx2HntwdO0JA27Wn9xx5zYijOe6B21ufrvsyv42auCO85+oFJWfE K2R/IpLle09GDx5tcEmMAHX6KSxpHmGuJmUPibHVbfep2aCh9lKaDqQR07gXXWK5/yU1Dx0r VVFRaHTasp9fZ9AmY4K9/BSA3VkQ8v3OrxNty3OdsrmTTzO91YszpdbjjEFZK53zXy6tUD2d e1i0kBBS6NLAAsqEtneplz88T/v7MpLmpY30N9gQU3QyRC50jJ7LU9RazMjUQY1WohVsR56d ORqFxS8ChhyJs7BI34vQusYHDTp6PnZHUppb9WIzjeWlC7Jc8lSBDlEWodmqQQgp5+6AfhTD kDv1a+W5+ncq+Uo63WHRiCPuyt4di4/0zo28RVcjtzlGBZtmz2EIC3vUfmoZbO/Gn6EKbYAn rzz3iU/JWV8DwQ+sZSGu0HmvYMt6t5SmqWQo/hyHtA7uF5Wxtu1lCgolSQw4t49ZuOyOnQi5 f8R3nE7lpVCSF1TT+h8kMvFPv3VG7KunyjHr3sEptYxQs4VRxqeirSuyBv1TyxT+LdTm6j4a mulOWf+YtFRAgIYyyN5YOepDEBv4LUM8Tz98lZiNMlFyRMNrsLV6Pv6SxhrMxbT6TNVS5D+6 UorTLotDZKp5+M7BTQRUY85qARAAsgMW71BIXRgxjYNCYQ3Xs8k3TfAvQRbHccky50h99TUY sqdULbsb3KhmY29raw1bgmyM0a4DGS1YKN7qazCDsdQlxIJp9t2YYdBKXVRzPCCsfWe1dK/q 66UVhRPP8EGZ4CmFYuPTxqGY+dGRInxCeap/xzbKdvmPm01Iw3YFjAE4PQ4hTMr/H76KoDbD cq62U50oKC83ca/PRRh2QqEqACvIH4BR7jueAZSPEDnzwxvVgzyeuhwqHY05QRK/wsKuhq7s UuYtmN92Fasbxbw2tbVLZfoidklikvZAmotg0dwcFTjSRGEg0Gr3p/xBzJWNavFZZ95Rj7Et db0lCt0HDSY5q4GMR+SrFbH+jzUY/ZqfGdZCBqo0cdPPp58krVgtIGR+ja2Mkva6ah94/oQN lnCOw3udS+Eb/aRcM6detZr7XOngvxsWolBrhwTQFT9D2NH6ryAuvKd6yyAFt3/e7r+HHtkU kOy27D7IpjngqP+b4EumELI/NxPgIqT69PQmo9IZaI/oRaKorYnDaZrMXViqDrFdD37XELwQ gmLoSm2VfbOYY7fap/AhPOgOYOSqg3/Nxcapv71yoBzRRxOc4FxmZ65mn+q3rEM27yRztBW9 AnCKIc66T2i92HqXCw6AgoBJRjBkI3QnEkPgohQkZdAb8o9WGVKpfmZKbYBo4pEAEQEAAcLB XwQYAQIACQUCVGPOagIbDAAKCRBoNZUwcMmSsJeCEACCh7P/aaOLKWQxcnw47p4phIVR6pVL e4IEdR7Jf7ZL00s3vKSNT+nRqdl1ugJx9Ymsp8kXKMk9GSfmZpuMQB9c6io1qZc6nW/3TtvK pNGz7KPPtaDzvKA4S5tfrWPnDr7n15AU5vsIZvgMjU42gkbemkjJwP0B1RkifIK60yQqAAlT YZ14P0dIPdIPIlfEPiAWcg5BtLQU4Wg3cNQdpWrCJ1E3m/RIlXy/2Y3YOVVohfSy+4kvvYU3 lXUdPb04UPw4VWwjcVZPg7cgR7Izion61bGHqVqURgSALt2yvHl7cr68NYoFkzbNsGsye9ft M9ozM23JSgMkRylPSXTeh5JIK9pz2+etco3AfLCKtaRVysjvpysukmWMTrx8QnI5Nn5MOlJj 1Ov4/50JY9pXzgIDVSrgy6LYSMc4vKZ3QfCY7ipLRORyalFDF3j5AGCMRENJjHPD6O7bl3Xo 4DzMID+8eucbXxKiNEbs21IqBZbbKdY1GkcEGTE7AnkA3Y6YB7I/j9mQ3hCgm5muJuhM/2Fr OPsw5tV/LmQ5GXH0JQ/TZXWygyRFyyI2FqNTx4WHqUn3yFj8rwTAU1tluRUYyeLy0ayUlKBH ybj0N71vWO936MqP6haFERzuPAIpxj2ezwu0xb1GjTk4ynna6h5GjnKgdfOWoRtoWndMZxbA z5cecg== Message-ID: <52518f09-7350-ebe9-7ddb-29095cd3a4d9@intel.com> Date: Tue, 6 Apr 2021 07:33:02 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 95A83E000108 X-Stat-Signature: 8mjpmmo3k8tmo83fedqb7tcwxybgww3a Received-SPF: none (intel.com>: No applicable sender policy available) receiver=imf21; identity=mailfrom; envelope-from=""; helo=mga05.intel.com; client-ip=192.55.52.43 X-HE-DKIM-Result: none/none X-HE-Tag: 1617719585-721994 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 4/6/21 12:44 AM, David Hildenbrand wrote: > On 02.04.21 17:26, Kirill A. Shutemov wrote: >> TDX architecture aims to provide resiliency against confidentiality an= d >> integrity attacks. Towards this goal, the TDX architecture helps enfor= ce >> the enabling of memory integrity for all TD-private memory. >> >> The CPU memory controller computes the integrity check value (MAC) for >> the data (cache line) during writes, and it stores the MAC with the >> memory as meta-data. A 28-bit MAC is stored in the ECC bits. >> >> Checking of memory integrity is performed during memory reads. If >> integrity check fails, CPU poisones cache line. >> >> On a subsequent consumption (read) of the poisoned data by software, >> there are two possible scenarios: >> >> =C2=A0 - Core determines that the execution can continue and it treats >> =C2=A0=C2=A0=C2=A0 poison with exception semantics signaled as a #MCE >> >> =C2=A0 - Core determines execution cannot continue,and it does an unbr= eakable >> =C2=A0=C2=A0=C2=A0 shutdown >> >> For more details, see Chapter 14 of Intel TDX Module EAS[1] >> >> As some of integrity check failures may lead to system shutdown host >> kernel must not allow any writes to TD-private memory. This requirment >> clashes with KVM design: KVM expects the guest memory to be mapped int= o >> host userspace (e.g. QEMU). >=20 > So what you are saying is that if QEMU would write to such memory, it > could crash the kernel? What a broken design. IMNHO, the broken design is mapping the memory to userspace in the first place. Why the heck would you actually expose something with the MMU to a context that can't possibly meaningfully access or safely write to it? This started with SEV. QEMU creates normal memory mappings with the SEV C-bit (encryption) disabled. The kernel plumbs those into NPT, but when those are instantiated, they have the C-bit set. So, we have mismatched mappings. Where does that lead? The two mappings not only differ in the encryption bit, causing one side to read gibberish if the other writes: they're not even cache coherent. That's the situation *TODAY*, even ignoring TDX. BTW, I'm pretty sure I know the answer to the "why would you expose this to userspace" question: it's what QEMU/KVM did alreadhy for non-encrypted memory, so this was the quickest way to get SEV working. So, I don't like the #MC either. But, this series is a step in the right direction for TDX *AND* SEV.