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 AAD9B33B972; Tue, 21 Oct 2025 14:01:35 +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=1761055297; cv=none; b=H4Oqb+U3PUK57I8i2m7r4mSrKfeWZC6bZ3x6Q0tmfiJqmb4fX/n+cVXasDNFjP3bLUxhH5j9aPwIJYNOY68zKIUlIHsso35cxNdD6n9b/m9eL97lZELvlWe46peSqfawyhJ9C4nIfnDbhFGjXFqihsRhve7gyE43AmHbJdAx9Rc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761055297; c=relaxed/simple; bh=Hbjc5gKyUpa1HOIxoR6MEzEBgkPttbDkGZX2GtTYuWQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=uZbpLrR1oKENgcPjraHbZKLQG/Xsk1skeye6i8NL2POJupf9oeeaLwzI+ZFdzM3WE76+rzg7upYf+7ni7g0daeiu7pwwGEWBJwHqtEMz09brjU1s2cuNRSKpQLPeXp9acorDpussIKAXJ8CCmee/vENsVKRKx9kJjdXlxHFCvH4= 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=C7VvXxDG; 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="C7VvXxDG" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1761055296; x=1792591296; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=Hbjc5gKyUpa1HOIxoR6MEzEBgkPttbDkGZX2GtTYuWQ=; b=C7VvXxDGNFXz98lohpTFTHWpJEco8Q8REbP281D78Omi3zPn0fiWme+R fK5ZN1gOrUakz7B5xs69YOzKEAuBNOsMhePSJtZ0eJbCfOR/5f+2Jdsw2 3ZlfmRGAdrXtfXnB8nH+PTXXDGXrHHDzbWNknFRYyw5GVgUfDcYXQFWFM VQEPpFnM0uPvJPkdD6qOVcBY8QHE4L7dB0D2KB537DmB9z+hwlCK+jwGd d4sBVUYtzAK+rzN/D/G//Azo5a4DP3ePdgxS1z+wN0zIZsmUj3FQjdA4K 3gu2TJ7VE5P85Dcy5VMm3XWOz9h8tuYqqi5l1ifMAZLOMMVLtQZ7qM+55 g==; X-CSE-ConnectionGUID: fG4T/XG/TKyJgcscwfW4sg== X-CSE-MsgGUID: sGVyOnLKTISpY/0o5RRY/w== X-IronPort-AV: E=McAfee;i="6800,10657,11586"; a="74299556" X-IronPort-AV: E=Sophos;i="6.19,245,1754982000"; d="scan'208";a="74299556" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by orvoesa105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Oct 2025 07:01:35 -0700 X-CSE-ConnectionGUID: 38z4pWhhQ5WGlf3stPnHBA== X-CSE-MsgGUID: ZHq1WzoHSg+J7gqZ1PtX6Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,245,1754982000"; d="scan'208";a="184078928" Received: from vverma7-desk1.amr.corp.intel.com (HELO [10.125.108.149]) ([10.125.108.149]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Oct 2025 07:01:34 -0700 Message-ID: <73a22a19-c492-4a75-8352-a4cfac47d812@intel.com> Date: Tue, 21 Oct 2025 07:01:33 -0700 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: [PATCH] x86/its: use Sapphire Rapids+ feature to opt out To: Jon Kohler , Pawan Gupta Cc: Thomas Gleixner , Borislav Petkov , Peter Zijlstra , Josh Poimboeuf , Jonathan Corbet , Ingo Molnar , Dave Hansen , "x86@kernel.org" , "H. Peter Anvin" , Brian Gerst , Brendan Jackman , "Ahmed S. Darwish" , Alexandre Chartre , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <20251017011253.2937710-1-jon@nutanix.com> <20251020194446.w2s5f6nr7i7vw4ve@desk> <20251020204026.a7xuhnagsqo4otpx@desk> <225134fd-033f-4d63-b88c-772179054694@intel.com> <20251020224159.xkhfs3phai5o6rzb@desk> <1D952EBC-CA16-49FE-8AD0-48BCE038332B@nutanix.com> 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: <1D952EBC-CA16-49FE-8AD0-48BCE038332B@nutanix.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/21/25 06:40, Jon Kohler wrote: > So to simplify it down: > A guest VM that updates to a ITS-enabled guest kernel sees performance > impacts on non-vulnerable hardware, when running on non-BHI_CTRL and/or > non-ITS_NO hypervisors, which is a very easy situation to get into, especially > on QEMU with live migration-enabled pools. By non-$FEATURE, do you mean that they chose to not enumerate those features, or that they are completely ignorant of them?