From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.15]) (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 164672F0671; Fri, 31 Oct 2025 16:55:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761929705; cv=none; b=Oyg+bDokTAr/RxlNdsYlPTBRGEoj/iiBS1YXEqTenSHf8eRdvW80vYxbQSSsqi2YNKUyh3bort8GgVM9kcvl2arV5ug3tvIvQlenrVjwuNAqurMm+dhFh0DgQycMlz1EoAzP0nIe4L6GfoUhLh5tbIF9lF6rhbCmvxM386g1RPA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761929705; c=relaxed/simple; bh=mE1Nacho2z2E7aj19mlpYVozO+U1hfyyMLxt4xW3lTs=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=S9jHlQiAWSbF2SG1XdzbbVceQUWbX2pfhMvEGaSRNiajTY17Dn6dKSXM1cNFc/cR8SUXTHdxbh+jZMZkJtcfEXCoZ7WnKkhLf+Ue1DWtyIx7kleZKt/4Hylrmc3v7zXPAHd2tTlD79NNWsPab2Hv3L4bPw+xJNwtcQxmHVXLJQU= 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=WVOJjmI5; arc=none smtp.client-ip=198.175.65.15 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="WVOJjmI5" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1761929704; x=1793465704; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=mE1Nacho2z2E7aj19mlpYVozO+U1hfyyMLxt4xW3lTs=; b=WVOJjmI54Oy4zOJsAF6W5J54zKw8CXFhZgIAVA6TYSt1q3UOsZP31Axp O8LI5QxPIPGWHaiJ7TXpxgGWaKhKRgt+B7oVkm6ZDOqgEsWlASYN5u/jW TUNF5uAvfcnQkaDTaB3kExpZaDhGqploN9WehpoDFDTHsBeA10bgwdFrK qXI3M0F3XKusd6j/cKeLjY8jxrvtLydJppGCw10YkrGJ0iIVkV0KOHSAN iKbQ2Z1li2O7gZq2PHaYpjDnAmypxURyA42rtvYuQQ+4biR4ZyMDNpwmG wLkoL0To7IILulLOxQhSe2B+wI4DPo27dRovY/GiWwUgoDSHHwp7Jnlie Q==; X-CSE-ConnectionGUID: hyqCD9IJQ5yTZBdRIXvQHQ== X-CSE-MsgGUID: UqdhOagySpmQ5V1b2nFyXw== X-IronPort-AV: E=McAfee;i="6800,10657,11599"; a="67750424" X-IronPort-AV: E=Sophos;i="6.19,269,1754982000"; d="scan'208";a="67750424" Received: from fmviesa001.fm.intel.com ([10.60.135.141]) by orvoesa107.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Oct 2025 09:55:03 -0700 X-CSE-ConnectionGUID: MIQ+2tf3QFiBgB8VYnsr8w== X-CSE-MsgGUID: jX0/fKWfROCUL4AocpFS5w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,269,1754982000"; d="scan'208";a="217119772" 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 09:55:02 -0700 Message-ID: Date: Fri, 31 Oct 2025 09:55:01 -0700 Precedence: bulk X-Mailing-List: linux-efi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v11 9/9] x86/cpu: Enable LASS by default during CPU initialization To: David Laight , Sohil Mehta Cc: Andy Lutomirski , "H. Peter Anvin" , the arch/x86 maintainers , Dave Hansen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Jonathan Corbet , 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> <20251029210310.1155449-10-sohil.mehta@intel.com> <789ADBB5-F7AC-4B08-B343-F23260FB8FBC@zytor.com> <13681100-ddc3-4ef0-bd13-744282324ff1@app.fastmail.com> <20251030211318.74d90c3f@pumpkin> 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: <20251030211318.74d90c3f@pumpkin> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/30/25 14:13, David Laight wrote: >> Unfortunately, CONFIG_X86_VSYSCALL_EMULATION defaults to y. Also, the >> default Vsyscall mode is XONLY. So even if vsyscalls are deprecated, >> there is a non-zero possibility someone would complain about it. > Presumably a command line parameter could be used to disable LASS > in order to enable vsyscall emulation? > > That might let LASS be enabled by default. Sure... There are a million ways to skin this cat. That's the problem. The compile switch is the smallest amount of code with the fewest implications to ABI or documentation that we can muster. All I'm saying is we should _start_ here, not _end_ here. If anyone agrees with that approach, acks would be appreciated.