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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3DAE5C433F5 for ; Mon, 7 Feb 2022 22:45:39 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 880F46B0073; Mon, 7 Feb 2022 17:45:38 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 82F386B0075; Mon, 7 Feb 2022 17:45:38 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6CFF66B0078; Mon, 7 Feb 2022 17:45:38 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0172.hostedemail.com [216.40.44.172]) by kanga.kvack.org (Postfix) with ESMTP id 5B9446B0073 for ; Mon, 7 Feb 2022 17:45:38 -0500 (EST) Received: from smtpin06.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 15E1A8249980 for ; Mon, 7 Feb 2022 22:45:38 +0000 (UTC) X-FDA: 79117467156.06.3E184AC Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by imf29.hostedemail.com (Postfix) with ESMTP id 39971120003 for ; Mon, 7 Feb 2022 22:45:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1644273937; x=1675809937; h=message-id:date:mime-version:to:cc:references:from: subject:in-reply-to:content-transfer-encoding; bh=/kRBeLG+E+e8Fa1In5ioSuQHyPxsmnGL5vggy8pd18g=; b=eD4w4btAOV/XjNk/mWqbvzm6WSHCcLnAdXTBzZi2drLwQ4VtU6axmtUd 5d28xEDmDdxCeZQVFbYCuRqt3QNS8+ycUt43NHOhlh+BtDqFWTfffGKdR 9WPWZMviXFAtVUzspJRoyxz86TwmkIhl6UGfAh8YH2IgPBoFrGro8qpBN y4ZqJBNC1qYeUP2AsKcI/Whynw3h7ifTXjD5zXcpyseaPwzOOqg4+FuSM vpWXRawavvzPoLrP3U3tfQbdXBgIRgaL9tTmDLViwDqMvUGTNvGMV0bni 2qOmWTFvqtq9hIm62BgvYSqo6U7yHScL8KwRepgFqfkjLeh7R/iiDsrCS A==; X-IronPort-AV: E=McAfee;i="6200,9189,10251"; a="249033233" X-IronPort-AV: E=Sophos;i="5.88,351,1635231600"; d="scan'208";a="249033233" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Feb 2022 14:45:30 -0800 X-IronPort-AV: E=Sophos;i="5.88,351,1635231600"; d="scan'208";a="525308323" Received: from hgrunes-mobl1.amr.corp.intel.com (HELO [10.251.3.57]) ([10.251.3.57]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Feb 2022 14:45:29 -0800 Message-ID: Date: Mon, 7 Feb 2022 14:45:26 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Content-Language: en-US To: Rick Edgecombe , x86@kernel.org, "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , "Ravi V . Shankar" , Dave Martin , Weijiang Yang , "Kirill A . Shutemov" , joao.moreira@intel.com, John Allen , kcc@google.com, eranian@google.com Cc: Yu-cheng Yu References: <20220130211838.8382-1-rick.p.edgecombe@intel.com> <20220130211838.8382-4-rick.p.edgecombe@intel.com> From: Dave Hansen Subject: Re: [PATCH 03/35] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) In-Reply-To: <20220130211838.8382-4-rick.p.edgecombe@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 39971120003 X-Rspam-User: nil Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=eD4w4btA; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf29.hostedemail.com: domain of dave.hansen@intel.com has no SPF policy when checking 192.55.52.115) smtp.mailfrom=dave.hansen@intel.com X-Stat-Signature: u7ydjzfjxnugef681w4msb1zafrrjcex X-Rspamd-Server: rspam08 X-HE-Tag: 1644273936-577483 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 1/30/22 13:18, Rick Edgecombe wrote: > --- a/arch/x86/kernel/cpu/cpuid-deps.c > +++ b/arch/x86/kernel/cpu/cpuid-deps.c > @@ -78,6 +78,7 @@ static const struct cpuid_dep cpuid_deps[] = { > { X86_FEATURE_XFD, X86_FEATURE_XSAVES }, > { X86_FEATURE_XFD, X86_FEATURE_XGETBV1 }, > { X86_FEATURE_AMX_TILE, X86_FEATURE_XFD }, > + { X86_FEATURE_SHSTK, X86_FEATURE_XSAVES }, > {} > }; Please add a chunk to the changelog that explains the dependency. This would suffice: To protect shadow stack state from malicious modification, the registers are only accessible in supervisor mode. This implementation context-switches the registers with XSAVES. Make X86_FEATURE_SHSTK depend on XSAVES. The XSAVES dependency is touched on in the documentation, but it's a bit buried in there.