From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.20]) (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 F14BC1F666A for ; Tue, 17 Dec 2024 15:06:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.20 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734447968; cv=none; b=EJIR4jWX0enHF05LJRgL5e/P6oIcNQsjlQnPX8tpPLZacEq91gax6gcSbQbVVj9R2FM8RLDjG2dY03yXZQDZDJoJNJXFEnbzIOojk3gMUHZsSSDBHCCglXsSQzlkTKpOwDh89MFHOJjxaNBsWlmk4pNxYrJJXR/xq6+vEVM+E2Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734447968; c=relaxed/simple; bh=VYgUBCCBapVjhIc533Rzulgo4zhAc4lsjV5YP7+N/ME=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=f0w4kB0YypPiXcLppXW4CVQw6Gd8b1NS6eIucDIsRLHKDyoG5ZU99eIEQX7MMi2Md3lIOiOKI+vytVJAFTiMYApNtm7zlCzBUlkts2+vpN0qHHY6s31AVkYfOVgES4kcXqmgJo4SfGpSX6dcZEto78O7jbqYoLT/eEXy0Vjtl+U= 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=cMN/gbzc; arc=none smtp.client-ip=198.175.65.20 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="cMN/gbzc" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1734447967; x=1765983967; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=VYgUBCCBapVjhIc533Rzulgo4zhAc4lsjV5YP7+N/ME=; b=cMN/gbzcw7eJOitt5bggoxilL3GQJ8p2Y88YLzRpyo/m8fDY0EVq5Z66 9MgUyO0YBIKlmGPUlOsP75+yAylMNVP8XP+baWlg/ImDKWR6KepAx1eUq FaH+rBAmUkeZU1kkLLI2E3fZB/n8BZnwAM29G7+9fj5hKzvT14Jc32jTC FaCh3n0MX9K3dyWnKzknGR/Oun4h+VGWD/ex3XFudzu3M1POV24ptHHSf 2vxb5/uSOHEfFv/iEPy5BdDbJ3Gisk6KyZrQKopkjO0uB+Avs/ua2bV1d pdfy9VpccsPSz+A9xlh540UaTGuEP2D16jBX+uKubduZnpKGyMNFPNGYC A==; X-CSE-ConnectionGUID: dLCWfVPKSMGWbaIiE8Pnag== X-CSE-MsgGUID: P3QB3eLMRPOQwEPONTB5QA== X-IronPort-AV: E=McAfee;i="6700,10204,11288"; a="34606919" X-IronPort-AV: E=Sophos;i="6.12,242,1728975600"; d="scan'208";a="34606919" Received: from fmviesa002.fm.intel.com ([10.60.135.142]) by orvoesa112.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Dec 2024 07:06:07 -0800 X-CSE-ConnectionGUID: 0HCoLGcPS36/QgdTdVVypA== X-CSE-MsgGUID: 9Y8BEF/kR+Sqb8PeC7alNw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,224,1728975600"; d="scan'208";a="120810844" Received: from ssimmeri-mobl2.amr.corp.intel.com (HELO [10.124.220.135]) ([10.124.220.135]) by fmviesa002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Dec 2024 07:06:05 -0800 Message-ID: Date: Tue, 17 Dec 2024 07:06:03 -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: [EXTERNAL] [PATCH 1/9] x86/kexec: Disable global pages before writing to control page To: David Woodhouse , "Kirill A. Shutemov" Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Eric Biederman , Sourabh Jain , Hari Bathini , Michael Ellerman , Thomas Zimmermann , Andrew Morton , Baoquan He , Yuntao Wang , David Kaplan , Tao Liu , Kai Huang , Ard Biesheuvel , Josh Poimboeuf , Breno Leitao , Wei Yang , Rong Xu , =?UTF-8?Q?Thomas_Wei=C3=9Fschuh?= , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, Simon Horman , Dave Young , Peter Zijlstra , bsz@amazon.de, nathan@kernel.org References: <20241216233704.3208607-1-dwmw2@infradead.org> <20241216233704.3208607-2-dwmw2@infradead.org> <28a98c27-7307-4698-9182-35e0d2cf12ad@intel.com> <7593b839a8c7d3122e08660ca2e957d834665005.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: <7593b839a8c7d3122e08660ca2e957d834665005.camel@infradead.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 12/17/24 06:56, David Woodhouse wrote: >> Anyway, I think we can leave the belt-and-suspenders programming in this >> case. A comment wouldn't hurt I guess. > I'm a little lost. In this case I don't see belt-and-suspenders > programming. We're not loading CR3 after clearing CR4.PGE just to be > paranoid about making really really sure the TLB is flushed. > > We're loading CR3 because we're switching from the kernel's page tables > to the new identity mapping set up for the relocate_kernel environment. Yes, agreed, that's another reason the CR3 write must stay. I hadn't even considered that part yet honestly.