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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 78477C433B4 for ; Tue, 6 Apr 2021 16:38:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4A0C7613D5 for ; Tue, 6 Apr 2021 16:38:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346494AbhDFQix (ORCPT ); Tue, 6 Apr 2021 12:38:53 -0400 Received: from mga17.intel.com ([192.55.52.151]:26090 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346415AbhDFQiv (ORCPT ); Tue, 6 Apr 2021 12:38:51 -0400 IronPort-SDR: sDW/IuPCXVeGxepljo3+dFOa+YXeCRKn5z8aJn5S1BzK/mYmtgg9lnHUKEb7BKkjqBSQJv9xLu b1D90ExeAjbQ== X-IronPort-AV: E=McAfee;i="6000,8403,9946"; a="173187019" X-IronPort-AV: E=Sophos;i="5.82,310,1613462400"; d="scan'208";a="173187019" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Apr 2021 09:38:43 -0700 IronPort-SDR: b7tcnY7BderJ4QK20eQOeLBL3v5QD7U2wMjolWHVlrsGq39waug5enz5f/u7g3fVhWrQrrAm6C mLPsJAkTa5NQ== X-IronPort-AV: E=Sophos;i="5.82,310,1613462400"; d="scan'208";a="447907689" Received: from hlalithk-mobl1.amr.corp.intel.com (HELO [10.209.146.228]) ([10.209.146.228]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 06 Apr 2021 09:38:42 -0700 Subject: Re: [RFC v1 25/26] x86/tdx: Make DMA pages shared To: "Kirill A. Shutemov" Cc: Kuppuswamy Sathyanarayanan , Peter Zijlstra , Andy Lutomirski , Andi Kleen , Kirill Shutemov , Kuppuswamy Sathyanarayanan , Dan Williams , Raj Ashok , Sean Christopherson , linux-kernel@vger.kernel.org, Kai Huang , Sean Christopherson References: <0bc9209a36760ee7c8591322327ddbfe87351b09.1612563142.git.sathyanarayanan.kuppuswamy@linux.intel.com> <20210406163150.cbmcybnu6hu5alk7@box> 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: <6065a93b-6bcd-2038-e994-6ec7b7b4c891@intel.com> Date: Tue, 6 Apr 2021 09:38:42 -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: <20210406163150.cbmcybnu6hu5alk7@box> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/6/21 9:31 AM, Kirill A. Shutemov wrote: > On Thu, Apr 01, 2021 at 02:01:15PM -0700, Dave Hansen wrote: >>> @@ -1977,8 +1978,8 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc) >>> struct cpa_data cpa; >>> int ret; >>> >>> - /* Nothing to do if memory encryption is not active */ >>> - if (!mem_encrypt_active()) >>> + /* Nothing to do if memory encryption and TDX are not active */ >>> + if (!mem_encrypt_active() && !is_tdx_guest()) >>> return 0; >> >> So, this is starting to look like the "enc" naming is wrong, or at least >> a little misleading. Should we be talking about "protection" or >> "guards" or something? > > Are you talking about the function argument or function name too? Yes, __set_memory_enc_dec() isn't really just doing "enc"ryption any more. >>> /* Should not be working on unaligned addresses */ >>> @@ -1988,8 +1989,14 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc) >>> memset(&cpa, 0, sizeof(cpa)); >>> cpa.vaddr = &addr; >>> cpa.numpages = numpages; >>> - cpa.mask_set = enc ? __pgprot(_PAGE_ENC) : __pgprot(0); >>> - cpa.mask_clr = enc ? __pgprot(0) : __pgprot(_PAGE_ENC); >>> + if (is_tdx_guest()) { >>> + cpa.mask_set = __pgprot(enc ? 0 : tdx_shared_mask()); >>> + cpa.mask_clr = __pgprot(enc ? tdx_shared_mask() : 0); >>> + } else { >>> + cpa.mask_set = __pgprot(enc ? _PAGE_ENC : 0); >>> + cpa.mask_clr = __pgprot(enc ? 0 : _PAGE_ENC); >>> + } >> >> OK, this is too hideous to live. It sucks that the TDX and SEV/SME bits >> are opposite polarity, but oh well. >> >> To me, this gets a lot clearer, and opens up room for commenting if you >> do something like: >> >> if (is_tdx_guest()) { >> mem_enc_bits = 0; >> mem_plain_bits = tdx_shared_mask(); >> } else { >> mem_enc_bits = _PAGE_ENC; >> mem_plain_bits = 0 >> } >> >> if (enc) { >> cpa.mask_set = mem_enc_bits; >> cpa.mask_clr = mem_plain_bits; // clear "plain" bits >> } else { >> >> cpa.mask_set = mem_plain_bits; >> cpa.mask_clr = mem_enc_bits; // clear encryption bits >> } > > I'm not convinced that your approach it clearer. If you add the missing > __pgprot() it going to as ugly as the original. > > But if a maintainer wants... :) Yes, please. I think my version (with the added __pgprot() conversions) clearly separates out the two thing that are going on. >>> cpa.pgd = init_mm.pgd; >>> >>> /* Must avoid aliasing mappings in the highmem code */ >>> @@ -1999,7 +2006,8 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc) >>> /* >>> * Before changing the encryption attribute, we need to flush caches. >>> */ >>> - cpa_flush(&cpa, !this_cpu_has(X86_FEATURE_SME_COHERENT)); >>> + if (!enc || !is_tdx_guest()) >>> + cpa_flush(&cpa, !this_cpu_has(X86_FEATURE_SME_COHERENT)); >> >> That "!enc" looks wrong to me. Caches would need to be flushed whenever >> encryption attributes *change*, not just when they are set. >> >> Also, cpa_flush() flushes caches *AND* the TLB. How does TDX manage to >> not need TLB flushes? > > I will double-check everthing, but I think we can skip *both* cpa_flush() > for private->shared conversion. VMM and TDX module will take care about > TLB and cache flush in response to MapGPA TDVMCALL. Oh, interesting. You might also want to double check if there are any more places where X86_FEATURE_SME_COHERENT and TDX have similar properties.