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 3EAE6C433E2 for ; Thu, 25 Mar 2021 15:52:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 00E1A61A21 for ; Thu, 25 Mar 2021 15:52:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229771AbhCYPwE (ORCPT ); Thu, 25 Mar 2021 11:52:04 -0400 Received: from mga02.intel.com ([134.134.136.20]:48480 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230228AbhCYPvo (ORCPT ); Thu, 25 Mar 2021 11:51:44 -0400 IronPort-SDR: +Hb5QyJEn954Y6zpaopSgrCZfNP02PdgOf7Fl09BUBZvCJLD87p7x+jAYM3su3B8+ld250YHL5 V2z+UndWd5TQ== X-IronPort-AV: E=McAfee;i="6000,8403,9934"; a="178079080" X-IronPort-AV: E=Sophos;i="5.81,277,1610438400"; d="scan'208";a="178079080" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2021 08:51:43 -0700 IronPort-SDR: 6m8atIa7mAPD7OzC2EyPSszUjlu5y7Td/6SyOPKJes6UWU8wzfO3M0e0TtnyyY16fwE214R+fH G6WIdpj49ZgA== X-IronPort-AV: E=Sophos;i="5.81,277,1610438400"; d="scan'208";a="391789207" Received: from jeffche1-mobl.amr.corp.intel.com (HELO [10.209.73.71]) ([10.209.73.71]) by orsmga002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2021 08:51:43 -0700 Subject: Re: [RFC Part2 PATCH 01/30] x86: Add the host SEV-SNP initialization support To: Brijesh Singh , linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org, linux-crypto@vger.kernel.org Cc: ak@linux.intel.com, herbert@gondor.apana.org.au, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Joerg Roedel , "H. Peter Anvin" , Tony Luck , "Peter Zijlstra (Intel)" , Paolo Bonzini , Tom Lendacky , David Rientjes , Sean Christopherson References: <20210324170436.31843-1-brijesh.singh@amd.com> <20210324170436.31843-2-brijesh.singh@amd.com> <696b8d42-8825-9df5-54a3-fa55f2d0f421@intel.com> <7cbafc72-f740-59b0-01f8-cd926ab7e010@amd.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: <8411ae2b-1a4a-d124-ffcb-ff351adac90e@intel.com> Date: Thu, 25 Mar 2021 08:51:42 -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: <7cbafc72-f740-59b0-01f8-cd926ab7e010@amd.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 3/25/21 8:31 AM, Brijesh Singh wrote: > > On 3/25/21 9:58 AM, Dave Hansen wrote: >>> +static int __init mem_encrypt_snp_init(void) >>> +{ >>> + if (!boot_cpu_has(X86_FEATURE_SEV_SNP)) >>> + return 1; >>> + >>> + if (rmptable_init()) { >>> + setup_clear_cpu_cap(X86_FEATURE_SEV_SNP); >>> + return 1; >>> + } >>> + >>> + static_branch_enable(&snp_enable_key); >>> + >>> + return 0; >>> +} >> Could you explain a bit why 'snp_enable_key' is needed in addition to >> X86_FEATURE_SEV_SNP? > > > The X86_FEATURE_SEV_SNP indicates that hardware supports the feature -- > this does not necessary means that SEV-SNP is enabled in the host. I think you're confusing the CPUID bit that initially populates X86_FEATURE_SEV_SNP with the X86_FEATURE bit. We clear X86_FEATURE bits all the time for features that the kernel turns off, even while the hardware supports it. Look at what we do in init_ia32_feat_ctl() for SGX, for instance. We then go on to use X86_FEATURE_SGX at runtime to see if SGX was disabled, even though the hardware supports it. >> For a lot of features, we just use cpu_feature_enabled(), which does >> both compile-time and static_cpu_has(). This whole series seems to lack >> compile-time disables for the code that it adds, like the code it adds >> to arch/x86/mm/fault.c or even mm/memory.c. > > Noted, I will add the #ifdef  to make sure that its compiled out when > the config does not have the AMD_MEM_ENCRYPTION enabled. IS_ENABLED() tends to be nicer for these things. Even better is if you coordinate these with your X86_FEATURE_SEV_SNP checks. Then, put X86_FEATURE_SEV_SNP in disabled-features.h, and you can use cpu_feature_enabled(X86_FEATURE_SEV_SNP) as both a (statically-patched) runtime *AND* compile-time check without an explicit #ifdefs.