From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.14]) (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 2A3CF1B87CA for ; Mon, 25 Nov 2024 19:13:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.14 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732561987; cv=none; b=on4d4irq/buxOo/9y7DzRjqqMb/kpdPYFqFmX21ReNgl7X2J2xc/MyRpFOic3l5eCiS27Fakw/C2bpIE0hP9/u4bERgaKsj2h1U8dKppB4c4V9jkyKBeN2H2PO6XYJVf2fgSQ0PO0Ap1z0lqTx8cqNHU1BvizvTUMTcAjCNEojA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732561987; c=relaxed/simple; bh=zGPvfdpZ67G+bPr0g9LrDZ6Reqrx79GMHAnSEOyTZZ4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=RxUeoSfh7nv4lqmty4MfsgHyqkmUYe2mRChDDzDtbsesBX2YsPw7OYHBdejreu7rwIIhEX6RrgY3BdPmGzaM0HaNy90O0qOQilhI5EhMpPyIs66SEsE6MKUswBsbJEjXZu0asvHdIIPYn8BbYzBMX8eGuQTQzJ3Hz183J7PbHIk= 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=kDJrhjUb; arc=none smtp.client-ip=198.175.65.14 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="kDJrhjUb" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1732561985; x=1764097985; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=zGPvfdpZ67G+bPr0g9LrDZ6Reqrx79GMHAnSEOyTZZ4=; b=kDJrhjUbowUvflk7AsfdqKMtZcNNfpumkrYZkL3MXb/N1MvyXF1k45ei U/yyArtlA0tw5pImy41vkFohbnT00s0MzwAUs1/gWK7f9OBLJRVYZNMsK hqz0vnGrw1CJmoBIidZ96V20u2Hot2XcLq94KyUwvIGwlDLF3hfXOajSd bH6WxedOXHKT0++ZL22kMCfKj16trizpGdLm6J4VVtckLto49lIO+yd7h Rf6bdVhEl20K8ebaqClEZMFbmrm4OWnowmaeeduNzwbhl8Zvjymm7HNEj Q0a9fdygk4F4zpzKjryxmfUnlgjukJSUF7X6opoJ5rNphXYDy8vaXrv02 A==; X-CSE-ConnectionGUID: kALpI7LUQPyJF3nCqftBpw== X-CSE-MsgGUID: nsWQjNw3SBa8SiKhZagm4w== X-IronPort-AV: E=McAfee;i="6700,10204,11267"; a="36471544" X-IronPort-AV: E=Sophos;i="6.12,183,1728975600"; d="scan'208";a="36471544" Received: from orviesa003.jf.intel.com ([10.64.159.143]) by orvoesa106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Nov 2024 11:13:04 -0800 X-CSE-ConnectionGUID: Z54pcM0MTIyu2QsvQ9M0+Q== X-CSE-MsgGUID: TuiUgQ0rSt++17Iftf8dZQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.11,199,1725346800"; d="scan'208";a="96423345" Received: from ccbilbre-mobl3.amr.corp.intel.com (HELO [10.124.221.82]) ([10.124.221.82]) by ORVIESA003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Nov 2024 11:13:03 -0800 Message-ID: <5633d50d-0d61-4d18-b43f-11311b5ec920@intel.com> Date: Mon, 25 Nov 2024 11:13:02 -0800 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: [RFC PATCH] x86/mm: Disable PTI for kernel_ident_mapping_init() To: David Woodhouse , kexec@lists.infradead.org, =?UTF-8?B?U2Now7ZuaGVyciwgSmFuIEgu?= , Rik van Riel Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , "Kirill A. Shutemov" , Kai Huang , Nikolay Borisov , linux-kernel@vger.kernel.org, Simon Horman , Dave Young , Peter Zijlstra , jpoimboe@kernel.org, bsz@amazon.de References: <20241125100815.2512-1-dwmw2@infradead.org> <20241125100815.2512-2-dwmw2@infradead.org> <8b7cd35ab5fec39b80eda8d5907b641af14c3272.camel@infradead.org> <7f75150e9d5d358c8fdc38b591f99a252071fba0.camel@infradead.org> <7e7cb9b21f17b345d8539962093d0c030cca3e34.camel@infradead.org> <88a87314-45ad-47f7-a93a-a9a53d7e8745@intel.com> <5d385e4c06ebd218cfdc20ef4f208ee4abcfa252.camel@infradead.org> 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: <5d385e4c06ebd218cfdc20ef4f208ee4abcfa252.camel@infradead.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 11/25/24 10:53, David Woodhouse wrote: >> I think we have a lot of software-available space in the page table >> pointer entries. What would folks think if we set a special bit in those >> p4d entries that said: >> >> "I don't need to be propagated to >> the user portion of the page tables." >> >> It would obviously get set in this code that you're trying to fix. It >> might _also_ be able to be set in in "_USR", like here: >> >> #define _KERNPG_TABLE_NOENC  (__PP|__RW|   0|___A|   0|___D|   0|   0) >> #define _PAGE_TABLE_NOENC    (__PP|__RW|_USR|___A|   0|___D|   0|   0) >> >> like: >> >> #define _USR _PAGE_USER|_PAGE_SW_WHATEVER > In fact, do we even need a separate bit? Any PTE without the _PAGE_USER > bit set clearly doesn't need to be mirrored into the user page > tables...? I can't think of any exceptions where this would break off the top of my head. It seems too simple to work. ;)