From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.8]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 48CC7330B1D; Fri, 31 Oct 2025 18:12:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.8 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761934376; cv=none; b=Cry2k4P3wuDnSeOPMAm1h0aOATgtc+wlZmOJDYqJobhY9cpZ4I4y7g6XuozWJQPETdw5qvhzBPAtE0QthqpPyyeg9Yubb3nrUW1e2hJ27odAmNrTtlwR8KiWqnWLNe2eZgjMoqB24e+faVnvXPgZA5GNrIJhFqiuPpSCGrcfOeU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761934376; c=relaxed/simple; bh=zcsY/9vIUhw+9jGtgQmPAFtoAzO7BoMmBaWoytIMxjE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=a/gpXKB6DZKWAHZy9FKgA/KgZTdizSeUzgnWMlW1c6rTJjmPWQcFimKgb/xHuFvzCiLhbXwECTzLyon/eqg+sd+7Ct6gEbmpf55A6zhGMDKvM52ThiYxl9np/PCu1aJ4+AemmRosHXQchfdoU/w7kDL/+YfstvAoxnmmJv9a91U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Zd24JM5O; arc=none smtp.client-ip=192.198.163.8 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Zd24JM5O" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1761934376; x=1793470376; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=zcsY/9vIUhw+9jGtgQmPAFtoAzO7BoMmBaWoytIMxjE=; b=Zd24JM5Oc9MSA9lmXVTwGXMmyYGve0qwg1vS92hBaUjeTKHhX5YrFhnH MP22vFiH2NxpW1ixIghITyl92lr/LbXR1KE1zAkNiGZbuTDUtoUWH/8Js DjAMs03c98fp1fa71tXVfk+qICL/sYGEvEo5nFxY69NaRJSG09wH6d+jN nakcdR1xDx22j4mvUYuERYJuujuWNtQWI2rQ29pRd2yVc9JKm29iN6maf kiNs402b/FnhHx249d3Vdf5P1bwgP3JjsjDnk7YR9pXBOo3b6NRgl5/9d R/sVqyUpojqCyuQHwzuF4i7PpzhcIwJe1mrkXVFtQi9PdqnOa5GQ0LTVH w==; X-CSE-ConnectionGUID: AcW4+f5TTH2EcMNMVKa3FQ== X-CSE-MsgGUID: h+mYulGVQMCYjFThA9197g== X-IronPort-AV: E=McAfee;i="6800,10657,11599"; a="81730925" X-IronPort-AV: E=Sophos;i="6.19,270,1754982000"; d="scan'208";a="81730925" Received: from fmviesa001.fm.intel.com ([10.60.135.141]) by fmvoesa102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Oct 2025 11:12:55 -0700 X-CSE-ConnectionGUID: 1VnXeolfTm6K3q91Rpumhw== X-CSE-MsgGUID: kCkcM2U8TsKJAlGuY5hf7g== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,270,1754982000"; d="scan'208";a="217136077" Received: from cmdeoliv-mobl4.amr.corp.intel.com (HELO [10.125.110.52]) ([10.125.110.52]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Oct 2025 11:12:53 -0700 Message-ID: Date: Fri, 31 Oct 2025 11:12:53 -0700 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v11 5/9] x86/efi: Disable LASS while mapping the EFI runtime services To: Sohil Mehta , Andy Lutomirski , the arch/x86 maintainers , Dave Hansen , Thomas Gleixner , Ingo Molnar , Borislav Petkov Cc: Jonathan Corbet , "H. Peter Anvin" , Josh Poimboeuf , "Peter Zijlstra (Intel)" , Ard Biesheuvel , "Kirill A . Shutemov" , Xin Li , David Woodhouse , Sean Christopherson , Rick P Edgecombe , Vegard Nossum , Andrew Cooper , Randy Dunlap , Geert Uytterhoeven , Kees Cook , Tony Luck , Alexander Shishkin , linux-doc@vger.kernel.org, Linux Kernel Mailing List , linux-efi@vger.kernel.org References: <20251029210310.1155449-1-sohil.mehta@intel.com> <20251029210310.1155449-6-sohil.mehta@intel.com> <3e9c4fdd-88a8-4597-9405-d865fb837d95@intel.com> <6dec8398-3f7c-44db-a30d-33593af0217f@intel.com> From: Dave Hansen Content-Language: en-US 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/aCccJK18ZwNjFhqr4MliQARAQABzUVEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gKEludGVsIFdvcmsgQWRkcmVzcykgPGRhdmUuaGFuc2VuQGludGVs LmNvbT7CwXgEEwECACIFAlQ+9J0CGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEGg1 lTBwyZKwLZUP/0dnbhDc229u2u6WtK1s1cSd9WsflGXGagkR6liJ4um3XCfYWDHvIdkHYC1t MNcVHFBwmQkawxsYvgO8kXT3SaFZe4ISfB4K4CL2qp4JO+nJdlFUbZI7cz/Td9z8nHjMcWYF IQuTsWOLs/LBMTs+ANumibtw6UkiGVD3dfHJAOPNApjVr+M0P/lVmTeP8w0uVcd2syiaU5jB aht9CYATn+ytFGWZnBEEQFnqcibIaOrmoBLu2b3fKJEd8Jp7NHDSIdrvrMjYynmc6sZKUqH2 I1qOevaa8jUg7wlLJAWGfIqnu85kkqrVOkbNbk4TPub7VOqA6qG5GCNEIv6ZY7HLYd/vAkVY E8Plzq/NwLAuOWxvGrOl7OPuwVeR4hBDfcrNb990MFPpjGgACzAZyjdmYoMu8j3/MAEW4P0z F5+EYJAOZ+z212y1pchNNauehORXgjrNKsZwxwKpPY9qb84E3O9KYpwfATsqOoQ6tTgr+1BR CCwP712H+E9U5HJ0iibN/CDZFVPL1bRerHziuwuQuvE0qWg0+0SChFe9oq0KAwEkVs6ZDMB2 P16MieEEQ6StQRlvy2YBv80L1TMl3T90Bo1UUn6ARXEpcbFE0/aORH/jEXcRteb+vuik5UGY 5TsyLYdPur3TXm7XDBdmmyQVJjnJKYK9AQxj95KlXLVO38lczsFNBFRjzmoBEACyAxbvUEhd GDGNg0JhDdezyTdN8C9BFsdxyTLnSH31NRiyp1QtuxvcqGZjb2trDVuCbIzRrgMZLVgo3upr MIOx1CXEgmn23Zhh0EpdVHM8IKx9Z7V0r+rrpRWFE8/wQZngKYVi49PGoZj50ZEifEJ5qn/H Nsp2+Y+bTUjDdgWMATg9DiFMyv8fvoqgNsNyrrZTnSgoLzdxr89FGHZCoSoAK8gfgFHuO54B lI8QOfPDG9WDPJ66HCodjTlBEr/Cwq6GruxS5i2Y33YVqxvFvDa1tUtl+iJ2SWKS9kCai2DR 3BwVONJEYSDQaven/EHMlY1q8Vln3lGPsS11vSUK3QcNJjmrgYxH5KsVsf6PNRj9mp8Z1kIG qjRx08+nnyStWC0gZH6NrYyS9rpqH3j+hA2WcI7De51L4Rv9pFwzp161mvtc6eC/GxaiUGuH BNAVP0PY0fqvIC68p3rLIAW3f97uv4ce2RSQ7LbsPsimOeCo/5vgS6YQsj83E+AipPr09Caj 0hloj+hFoqiticNpmsxdWKoOsV0PftcQvBCCYuhKbZV9s5hjt9qn8CE86A5g5KqDf83Fxqm/ vXKgHNFHE5zgXGZnrmaf6resQzbvJHO0Fb0CcIohzrpPaL3YepcLDoCCgElGMGQjdCcSQ+Ci FCRl0Bvyj1YZUql+ZkptgGjikQARAQABwsFfBBgBAgAJBQJUY85qAhsMAAoJEGg1lTBwyZKw l4IQAIKHs/9po4spZDFyfDjunimEhVHqlUt7ggR1Hsl/tkvTSze8pI1P6dGp2XW6AnH1iayn yRcoyT0ZJ+Zmm4xAH1zqKjWplzqdb/dO28qk0bPso8+1oPO8oDhLm1+tY+cOvufXkBTm+whm +AyNTjaCRt6aSMnA/QHVGSJ8grrTJCoACVNhnXg/R0g90g8iV8Q+IBZyDkG0tBThaDdw1B2l asInUTeb9EiVfL/Zjdg5VWiF9LL7iS+9hTeVdR09vThQ/DhVbCNxVk+DtyBHsjOKifrVsYep WpRGBIAu3bK8eXtyvrw1igWTNs2wazJ71+0z2jMzbclKAyRHKU9JdN6Hkkgr2nPb561yjcB8 sIq1pFXKyO+nKy6SZYxOvHxCcjk2fkw6UmPU6/j/nQlj2lfOAgNVKuDLothIxzi8pndB8Jju KktE5HJqUUMXePkAYIxEQ0mMc8Po7tuXdejgPMwgP7x65xtfEqI0RuzbUioFltsp1jUaRwQZ MTsCeQDdjpgHsj+P2ZDeEKCbma4m6Ez/YWs4+zDm1X8uZDkZcfQlD9NldbKDJEXLIjYWo1PH hYepSffIWPyvBMBTW2W5FRjJ4vLRrJSUoEfJuPQ3vW9Y73foyo/qFoURHO48AinGPZ7PC7TF vUaNOTjKedrqHkaOcqB185ahG2had0xnFsDPlx5y In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/31/25 11:03, Sohil Mehta wrote: >> Deferring is a good idea. I was just asking for the same thing for the >> CR pinning enforcement. The earlier we try to do these things, the more >> we just trip over ourselves. > I had suggested deferring as well to Kirill when I was reviewing the > series. He preferred to enable LASS with other similar features such as > SMAP, SMEP. > > One other thing to consider: > > Doing it in identify_cpu() makes it easy for all the APs to program > their CR4.LASS bit. If we were to defer it, we would need some > additional work to setup all the APs. That's true. We'd need an smp_call_function() of some kind. *But*, once that is in place, it's hopefully just a matter of moving that one line of code per feature from identify_cpu() over to the new function. > Do we already do this for something else? That would make it easier to > tag along. We don't do it for anything else that I can think of. But there's a pretty broad set of things that are for "security" that aren't necessary while you're just running trusted ring0 code: * SMAP/SMEP * CR pinning itself * MSR_IA32_SPEC_CTRL * MSR_IA32_TSX_CTRL They just haven't mattered until now because they don't have any practical effect until you actually have code running on _PAGE_USER mappings trying to attack the kernel.