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 58200C54E4A for ; Fri, 8 Mar 2024 15:24:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C07816B03A5; Fri, 8 Mar 2024 10:24:05 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id B8E6C6B03A6; Fri, 8 Mar 2024 10:24:05 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A09556B03A7; Fri, 8 Mar 2024 10:24:05 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 79B2F6B03A5 for ; Fri, 8 Mar 2024 10:24:05 -0500 (EST) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 4878740C38 for ; Fri, 8 Mar 2024 15:24:05 +0000 (UTC) X-FDA: 81874242450.22.876F3CF Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.16]) by imf12.hostedemail.com (Postfix) with ESMTP id 42B5840005 for ; Fri, 8 Mar 2024 15:24:00 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=d2kURqAb; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf12.hostedemail.com: domain of dave.hansen@intel.com designates 192.198.163.16 as permitted sender) smtp.mailfrom=dave.hansen@intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1709911442; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=u8T17NYzEuAkboRvcuTr0+eQzl1hJHiDAxPi1WwB8vQ=; b=okdGx+sc84hHwWclosBjczEtF+L++rner8KvM7vHlQaViTfx9N5qEBllDnJrARnZELfFON ghg9kr9d6TES9mT31yIpU2GeSL72AMysGlBK+K554I2EdKuI0Zv3C+ld2jTdduvDkA2OII 1hExDTFhBBD5AkKkwSSaW/MyxJj0zXA= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=d2kURqAb; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf12.hostedemail.com: domain of dave.hansen@intel.com designates 192.198.163.16 as permitted sender) smtp.mailfrom=dave.hansen@intel.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1709911442; a=rsa-sha256; cv=none; b=lXP8clYK8JsRqRUXoFDWuQ30qkMWAhmAt5HHOd8b/t1Qa8rZxMSClIYK95vHHyVr5KRkCp k8nWsPjqsFWTfCMLQLyzGB+xmDePO0DLEV153cFkTeTlSeYT62mbTWNJG0k5Cw2kr32ObA jg+HeYyA7O/iR93SsQHVhkOAQNalztQ= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1709911441; x=1741447441; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=D7fa23jwhdR/0Ruut/uLrO8UufA0ppltESXABl7U58o=; b=d2kURqAboJKIH9Z2mikUAHe1QqegYM+lHJiDz3EpHvmSzcBNIhiW6rNC OJ1iXvyLr/o3QeGWmHPnZH3mv9d/DN6qYLyrdxH5yQ0kOcGTo2Tr0vtlk FpgGfuciQqJMA+nQVbGlcn2aaUeZ7PxNpMvD6w1GCQ62AQjKX2yQqEVsX H0gES8IiuRxONwixY2voqjI6Z8BrEqM3/vFUdnsA55X/Ygft+l1qyBzj8 FTQNncsZp9wmiICulGF4ALdpxV6ai+86uUJ2SQBEL+cTmVUSLbEadlmIT hRI6Ptz3U6OjcpYE4E1wXuTeG3B9yzbBh1J98YrxbBLu+QAGKuafoZmlE Q==; X-IronPort-AV: E=McAfee;i="6600,9927,11006"; a="5234627" X-IronPort-AV: E=Sophos;i="6.07,109,1708416000"; d="scan'208";a="5234627" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by fmvoesa110.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Mar 2024 07:23:59 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.07,109,1708416000"; d="scan'208";a="47949762" Received: from mananmeh-mobl.amr.corp.intel.com (HELO [10.212.139.209]) ([10.212.139.209]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Mar 2024 07:23:59 -0800 Message-ID: <35b670e2-9ef5-4d3a-b6ea-f8016dfa088d@intel.com> Date: Fri, 8 Mar 2024 07:23:58 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 2/3] x86/mm: make sure LAM is up-to-date during context switching Content-Language: en-US To: Andy Lutomirski , Yosry Ahmed , Andrew Morton Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "Peter Zijlstra (Intel)" , "Kirill A. Shutemov" , the arch/x86 maintainers , linux-mm@kvack.org, Linux Kernel Mailing List References: <20240307133916.3782068-1-yosryahmed@google.com> <20240307133916.3782068-3-yosryahmed@google.com> <420fcb06-c3c3-4e8f-a82d-be2fb2ef444d@app.fastmail.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/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: <420fcb06-c3c3-4e8f-a82d-be2fb2ef444d@app.fastmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 42B5840005 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: emzso8u64c8p5fgo7pnyh51jeyxah8dy X-HE-Tag: 1709911440-338656 X-HE-Meta: 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 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: List-Subscribe: List-Unsubscribe: On 3/7/24 17:34, Andy Lutomirski wrote: >> Fix this by making sure we write a new CR3 if LAM is not >> up-to-date. No problems were observed in practice, this was found >> by code inspection. > I think it should be fixed with a much bigger hammer: explicit IPIs. > Just don't ever let it get out of date, like install_ldt(). I guess it matters whether the thing that matters is having a persistent inconsistency or a temporary one. IPIs will definitely turn a permanent one into a temporary one. But this is all easier to reason about if we can get rid of even the temporary inconsistency. Wouldn't this be even simpler than IPIs? static inline unsigned long set_tlbstate_lam_mode(struct mm_struct *mm) { unsigned long lam = READ_ONCE(mm->context.lam_cr3_mask); + /* LAM is for userspace only. Ignore it for kernel threads: */ + if (tsk->flags & PF_KTHREAD) + return 0; this_cpu_write(cpu_tlbstate.lam, lam >> X86_CR3_LAM_U57_BIT); this_cpu_write(tlbstate_untag_mask, mm->context.untag_mask); return lam; }