From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.13]) (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 5AE261531C1 for ; Mon, 25 Nov 2024 18:31:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.13 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732559478; cv=none; b=ZXkupbo5YrDXUDOdLM5Iil3PmqIP8cO6w72LwtjSvxIU3fN8tX5SqQnbdNvS+7uPtQlBHjX00YzFSlJAPDS8dj3eriVvZvsogPJHHx90dzElaIlgHsYlyr5+KCF8jQpKRLj6vcFa+WALdgbfwcHU/nIUBqUIAS++DcMmo7X78fY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732559478; c=relaxed/simple; bh=05aT/5aPIFQshJGnfctNoSldWiTBPVnYEKVqSs+M9mo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=mR9r+IQ7WVtoGE9TcZR8ve8ybRZL+IFWsozGl1rpDdzGs7UIZZU8YVzCYB8sAvS3r2DXI0KLHRIBNHjtn5Y+2E8ykiW6qpooRjVWv6lLRzkIQgrRf1TQO3WU5OdblUgtlSpeE2L3BbZ0ScPRcPRobIruOE16iQb04CGMWReKhBs= 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=mQSfzSyn; arc=none smtp.client-ip=198.175.65.13 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="mQSfzSyn" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1732559477; x=1764095477; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=05aT/5aPIFQshJGnfctNoSldWiTBPVnYEKVqSs+M9mo=; b=mQSfzSynWf0du9yud0Ix2w/odQvZwRu4LWdmIrwyr6A5mfXxUQAQcUB8 qbKwqF2jLHeafkfp/bqFZq+Niicw7WR3UdBbe76gNUjUhKBc/mGezmF9d njR8gRchRhXBIFLDZUc5cl/sN7xupO+QMhbsS8kOm9QSkm5jifLd3RWZp QD+w2vUBVX5lFNC0oWvPbe2UbIVin2+UZZMuQ8ajPu4desLtlR+AOCzZG AyMezc9RZgR+RLPuqU4tWLPAgXcrUG38AugBEZKzuu4WUDbJBabpORrT3 p0bJcR+Fua8i3zZiLOsx3c7VqJpwSKNBWSglw1nrdZJGVtyQa10X0dLpq g==; X-CSE-ConnectionGUID: np9GJf03T1iOi0I4BZnulA== X-CSE-MsgGUID: WZTsEDDkTv2FKqs5BOWT7g== X-IronPort-AV: E=McAfee;i="6700,10204,11267"; a="43752760" X-IronPort-AV: E=Sophos;i="6.12,183,1728975600"; d="scan'208";a="43752760" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by orvoesa105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Nov 2024 10:31:16 -0800 X-CSE-ConnectionGUID: K4zftO7qSGmoQUim6/vCGg== X-CSE-MsgGUID: 57px81xIQHGy4zwn8Pgt9Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,183,1728975600"; d="scan'208";a="95442025" Received: from ccbilbre-mobl3.amr.corp.intel.com (HELO [10.124.221.35]) ([10.124.221.35]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Nov 2024 10:31:15 -0800 Message-ID: <88a87314-45ad-47f7-a93a-a9a53d7e8745@intel.com> Date: Mon, 25 Nov 2024 10:31:13 -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> 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: <7e7cb9b21f17b345d8539962093d0c030cca3e34.camel@infradead.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/25/24 09:05, David Woodhouse wrote: > Not sure I like this very much, but it works, and mirrors what > arch/x86/boot/compressed/ident_map_64.c already does. I don't like it much, either. arch/x86/boot/compressed/ is already on the road to sharing no code with the core kernel and it's full of horrors. It should be an example of what *not* to do. ;) 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