From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.9]) (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 9AA572E6CBE for ; Fri, 24 Oct 2025 20:14:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761336893; cv=none; b=u4Pk+asChSBJSLmd7FVwmbohAuQoeb2uf4bTb7hnxaFl+Dtt3sYv5bGGYp+ewJgLhXk4KG/pVwgNWDS1XNgj0piNrrvAcaLxNvLVmTLAiiYfM1zndOw83LY1tcFpkSM7qJq2Vh7CB0AuGBAAfUWI1Z+qCm7jdwLLaOx2HWSi68I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761336893; c=relaxed/simple; bh=cg/YObBlYETxR8RXHfEISwwC9KkMJl2BXmchL+rYBv0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=MHsx4WMPCOvLD7nSHbWzZwn1s8u1OZnE7lwhcQnLGPccGnBAm/RbwKan+LtCIO7urR4iCTRgXnl15Kwi4XssbHZY9YD+b8WmNgfW+7TtN8YVyqB0Fjadye1qmVuBIlsn488Rr4gTJk3GQTfzUJWFyaVAaBJEKIl9su2HWOz7mzU= 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=GGadB26c; arc=none smtp.client-ip=198.175.65.9 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="GGadB26c" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1761336892; x=1792872892; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=cg/YObBlYETxR8RXHfEISwwC9KkMJl2BXmchL+rYBv0=; b=GGadB26cfdkOHE5ou6SXODzDottALel3drA6IAgLETugFJUvRp9OBYyb lT4j0DPZnebZZ850WdnXf0u2uRYsv1M7AR19MVxfFmeBqd1piUBHSGfiF hHE13XTjL6SuoI0zBt63yIsbp19G8l3T7QuD05IcxioEqyIshQXPuHm8+ hwNzNbo5y/ku2DxyuHjtheGKOysT5JBJrY5KD8azDx7+7OVexbmBj7Jrc r6Uu2oougGY4QcxW1hLIipWthZV6K9d4I6WhhVWUXYNcqspeCeOF0WYzv DZbSMIXPSpGcfyXvJNTBUe/lYVPhvJ0hQ3FgB3l12snrXUy7JigS2jAJK g==; X-CSE-ConnectionGUID: 6HOGpfSSRpuHhnvOtC6WrA== X-CSE-MsgGUID: 5sxL5BFBQV+xpHeLEzdEeA== X-IronPort-AV: E=McAfee;i="6800,10657,11586"; a="86153584" X-IronPort-AV: E=Sophos;i="6.19,253,1754982000"; d="scan'208";a="86153584" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by orvoesa101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Oct 2025 13:14:51 -0700 X-CSE-ConnectionGUID: SvR/jMdJSf6U0cY4FK2Swg== X-CSE-MsgGUID: yQ/qLSV+QLuXhXVHkKaCaQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,253,1754982000"; d="scan'208";a="188815549" Received: from aschofie-mobl2.amr.corp.intel.com (HELO [10.125.109.44]) ([10.125.109.44]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Oct 2025 13:14:51 -0700 Message-ID: <45c85e40-d049-4242-a251-d541e60d6e7d@intel.com> Date: Fri, 24 Oct 2025 13:14:50 -0700 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 00/21] Runtime TDX Module update support To: Sean Christopherson , dan.j.williams@intel.com Cc: Chao Gao , Vishal Annapurve , Elena Reshetova , "linux-coco@lists.linux.dev" , "linux-kernel@vger.kernel.org" , "x86@kernel.org" , Reinette Chatre , Ira Weiny , Kai Huang , "yilun.xu@linux.intel.com" , "sagis@google.com" , "paulmck@kernel.org" , "nik.borisov@suse.com" , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Ingo Molnar , "Kirill A. Shutemov" , Paolo Bonzini , Rick P Edgecombe , Thomas Gleixner References: <68fbd63450c7c_10e910021@dwillia2-mobl4.notmuch> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/24/25 13:00, Sean Christopherson wrote: > C'mon people (especially the Google folks), this is the ***exact*** > same problem as certificate updates for SNP[1]. Y'all suggested > holding a lock across a userspace exit back then, and Dan's analysis > confirms my reaction from back then that "Holding a lock across an > exit to userspace seems wildly unsafe."[2] > > In the end, it took more time to understand the problem then to > sketch out and test a solution[3]. > > Unless this somehow puts the host (kernel) at risk, this is a > userspace problem. If there's an similar SEV-SNP problem and accepted solution punted to userspace that TDX can leverage, I'm 100% on board with that. Let's do that.