From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.17]) (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 9A08A4F200 for ; Mon, 1 Apr 2024 17:56:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711994178; cv=none; b=nmGNLRLyz9odMudE2dQXEoee8Yc+/vQC+6UhaYjOjkoJeLiYJassDb4GbmztuHwI+J+UJ756aU3tO9hyknVy3GiGiTYEWiTBglBqIL3OJoYpZsTMEJiHWQ8/50UIwNJUpvQ26ixPBnafZcjNakqElFnQ3nW+Zfpyii9IlQCfXsY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711994178; c=relaxed/simple; bh=K8ZYwb8nVuPFiuvTlpHRAIwMR+3U3ALosS7AP6ycdZI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=uh4zS+azvoazyltn6jOMNYosCtt2tSn0SMvn9LdNFr5Qgo0l0TsuuBK+zNnERBf0STkP3t4GS9JYkeYg4FIHfISvz8y+DbTqsmecvppfQku7Ry0g/xTgWAlAPm80j9FrALZd/BSWCgN52I0eIF6wVd+XrvvjglHNp/4Y70BK9sc= 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=NeyxgSbt; arc=none smtp.client-ip=198.175.65.17 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="NeyxgSbt" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1711994177; x=1743530177; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=K8ZYwb8nVuPFiuvTlpHRAIwMR+3U3ALosS7AP6ycdZI=; b=NeyxgSbt55MImhV4ZPznulnI63Ql44dvMAmJne62epvUTrwLnlMzKKQE rnnWhPHuCe7GiHGsg/PH6U/5HlCyJG3izDkxyuI55PS0AqRT7g7Ydquyf 83tG3ZyNrAtJ+RLnGjJD7wMZTzELf5Oxl/hwKifCxi5/tgqEpQ/vM4Gok oHMSc05U60o+HpEY3oQ3OdLDSJPmFYUjgQQ+AdLuqVIaQ3fxx+PYsZwv6 RhEZbDQBlLWPdiG3NzZ/DIBn9qCpWtHXC42a94AG9oof5C7eAzIFO0tF4 bdUdXlCH3dCLg/6Js4TkSGQ7FdtD54vOvjfCy2E73rWPKIsIbDIfFrYg3 Q==; X-CSE-ConnectionGUID: NYOfrDdDTmauMoA0pTPK/w== X-CSE-MsgGUID: 7278nQCSTWydya/oUHVS3w== X-IronPort-AV: E=McAfee;i="6600,9927,11031"; a="7250876" X-IronPort-AV: E=Sophos;i="6.07,172,1708416000"; d="scan'208";a="7250876" Received: from fmviesa002.fm.intel.com ([10.60.135.142]) by orvoesa109.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Apr 2024 10:56:16 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.07,172,1708416000"; d="scan'208";a="40945848" Received: from mminuddi-mobl1.amr.corp.intel.com (HELO [10.209.48.250]) ([10.209.48.250]) by fmviesa002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Apr 2024 10:56:15 -0700 Message-ID: <8ee463af-fdbf-4514-bb6e-bf2fd61fbc06@intel.com> Date: Mon, 1 Apr 2024 10:56:14 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/1] x86/mm/pae: Align up pteval_t, pmdval_t and pudval_t to avoid split locks To: Javier Pello , linux-kernel@vger.kernel.org Cc: x86@kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" References: <20240401185451.6897208962d3fc47a12ffb5a@otheo.eu> <20240401185712.a80deeb2fddeded0ad42cc04@otheo.eu> Content-Language: en-US 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/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: <20240401185712.a80deeb2fddeded0ad42cc04@otheo.eu> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/1/24 09:57, Javier Pello wrote: > -typedef u64 pteval_t; > -typedef u64 pmdval_t; > -typedef u64 pudval_t; > -typedef u64 p4dval_t; > -typedef u64 pgdval_t; > -typedef u64 pgprotval_t; > +/* > + * Variables of these types are subject to atomic compare-and-exchange > + * operations, so they have to be properly aligned to avoid split locks. > + */ > +typedef u64 pteval_t __aligned(8); > +typedef u64 pmdval_t __aligned(8); > +typedef u64 pudval_t __aligned(8); > +typedef u64 p4dval_t __aligned(8); > +typedef u64 pgdval_t __aligned(8); > +typedef u64 pgprotval_t __aligned(8); First of all, how is it that you're running a PAE kernel on new, 64-bit hardware? That's rather odd. The case that you're hitting is actually an on-stack pmd_t. The fun part is that it's not shared and doesn't even _need_ atomics. I think it's just using pmd_populate() because it's convenient. I'd honestly much rather just disable split lock support in 32-bit builds than mess with this stuff. You really shouldn't be running 32-but kernels on this hardware.