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 9078DC5475B for ; Tue, 12 Mar 2024 00:53:42 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 17ED56B00AA; Mon, 11 Mar 2024 20:53:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 155E56B00BB; Mon, 11 Mar 2024 20:53:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 01C986B00BD; Mon, 11 Mar 2024 20:53:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id E55686B00AA for ; Mon, 11 Mar 2024 20:53:41 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id BB09A80E17 for ; Tue, 12 Mar 2024 00:53:41 +0000 (UTC) X-FDA: 81886564242.20.909BC29 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.16]) by imf07.hostedemail.com (Postfix) with ESMTP id B136B40008 for ; Tue, 12 Mar 2024 00:53:38 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=CqfEu1Y7; spf=pass (imf07.hostedemail.com: domain of dave.hansen@intel.com designates 192.198.163.16 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (policy=none) header.from=intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1710204820; 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=XAXtTfEXGKv53KCC9cMlFPbHyVA7kEAHQrIVYEVEo1E=; b=n5vD2fRI/w9sjDWHccyH/V4177OCIDbLnpDCnyDcHpx4ebQkWkqyDgIHMnSv+Fzr0rp1IQ 7Sq61G/x9e4UNscNiS2TJsrpIkpwjNhiO1gBWW3IA/pGJ+bygxT0xO7Wez3m+WrZZH4xF6 9FIfdlv6Nd+izODK2MzDGZzI7nHAkkQ= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1710204820; a=rsa-sha256; cv=none; b=wRfOJ3Bc7vlzX1LZVRJubh+Xgnfx37KhZ+vz6Z1dUr8+NXx7VjJpucPqmgrsbGj9VAgmP9 xRPdFeQAWF0gGcFkkNDqOe4sJtH6XULuycIZ5LCeL4EyQ4rJTzzTz9pNmBRA5FdDQNCXKi OdthMEWnotCrL1SSGkIQVmOCWGXinRk= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=CqfEu1Y7; spf=pass (imf07.hostedemail.com: domain of dave.hansen@intel.com designates 192.198.163.16 as permitted sender) smtp.mailfrom=dave.hansen@intel.com; dmarc=pass (policy=none) header.from=intel.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1710204819; x=1741740819; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=C6LtKzzQJay8DHvjH/vS7Shki8otvBwfa/Ly0CnqENw=; b=CqfEu1Y7+K7fFEuLPnn844tjwGd0UBt5HYd6vRUGbhoXnLg4NK37m3Qw gcH+annXx0POQmTkCYKjTUH/X/5FI0dPskofMwlRgKEbYNNROOxNU3zHp DQ1lZ6X29/aozEM/Qzfpmzj8NZGqaEAjS0xcp0cUzZ9n1h3cF1gaKLTs1 Ef5hSuyxxgwtYUSuR60o4DDOAc1SnUGwtyzlWJE/6pyk88Hf29p4C6Ph1 K7t+ayVY7OOqTkaMuvn4Ja0yuhiHWcThHHHA6QDn4ZOlmzZ/7+NNRpRlc atHHlvqw18sLEI3Za0Mh+MOLIzDseGFoDgcAULadBvO2COzrgB45w0pTW Q==; X-IronPort-AV: E=McAfee;i="6600,9927,11010"; a="5501228" X-IronPort-AV: E=Sophos;i="6.07,118,1708416000"; d="scan'208";a="5501228" Received: from fmviesa006.fm.intel.com ([10.60.135.146]) by fmvoesa110.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Mar 2024 17:53:36 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.07,118,1708416000"; d="scan'208";a="11422641" Received: from siverson-mobl1.amr.corp.intel.com (HELO [10.209.94.13]) ([10.209.94.13]) by fmviesa006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Mar 2024 17:53:32 -0700 Message-ID: Date: Mon, 11 Mar 2024 17:53:33 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 11/14] x86: add support for Dynamic Kernel Stacks Content-Language: en-US To: Nadav Amit , Andy Lutomirski Cc: Pasha Tatashin , Linux Kernel Mailing List , linux-mm , Andrew Morton , the arch/x86 maintainers , Borislav Petkov , Christian Brauner , bristot@redhat.com, Ben Segall , Dave Hansen , dianders@chromium.org, dietmar.eggemann@arm.com, eric.devolder@oracle.com, hca@linux.ibm.com, "hch@infradead.org" , "H. Peter Anvin" , Jacob Pan , Jason Gunthorpe , jpoimboe@kernel.org, Joerg Roedel , juri.lelli@redhat.com, Kent Overstreet , kinseyho@google.com, "Kirill A. Shutemov" , lstoakes@gmail.com, mgorman@suse.de, mic@digikod.net, michael.christie@oracle.com, Ingo Molnar , mjguzik@gmail.com, "Michael S. Tsirkin" , Nicholas Piggin , "Peter Zijlstra (Intel)" , Petr Mladek , Rick P Edgecombe , Steven Rostedt , Suren Baghdasaryan , Thomas Gleixner , Uladzislau Rezki , vincent.guittot@linaro.org, vschneid@redhat.com References: <20240311164638.2015063-1-pasha.tatashin@soleen.com> <20240311164638.2015063-12-pasha.tatashin@soleen.com> <3e180c07-53db-4acb-a75c-1a33447d81af@app.fastmail.com> <08EFDEDB-7BBB-4D9C-B7E5-D7370EC609BE@gmail.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: <08EFDEDB-7BBB-4D9C-B7E5-D7370EC609BE@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: B136B40008 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: xcdbu959uq9kkjg9cj3f7j3559ffq5j4 X-HE-Tag: 1710204818-337905 X-HE-Meta: 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 6hUXPQgG qaGkq/5NmaxdHItlJFbmr0gVgsA== 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 3/11/24 16:56, Nadav Amit wrote: > So you can look on the dirty-bit, which is not being set > speculatively and save yourself one problem. Define "set speculatively". :) > If software on one logical processor writes to a page while software > on another logical processor concurrently clears the R/W flag in the > paging-structure entry that maps the page, execution on some > processors may result in the entry’s dirty flag being set (due to the > write on the first logical processor) and the entry’s R/W flag being > clear (due to the update to the entry on the second logical > processor). In other words, you'll see both a fault *AND* the dirty bit. The write never retired and the dirty bit is set. Does that count as being set speculatively? That's just the behavior that the SDM explicitly admits to.