From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.18]) (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 758A11E9B3F for ; Thu, 30 Oct 2025 15:00:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761836449; cv=none; b=IASEmJW8HCjL2KP5+fJ9enteXdFbzeHVHNUOM5jj6OTO8+3W8Ye2d6I4wntp8NbkUsoYeX08qIXZxkhdUsv7O8BhfLTDsTJAE9rWtXFa/Iv9YZbZJLw+4WldLWAgMwxn21Diy5/qlCUELyG2cmi61kbetiBmxMAWtPgLp5Kk/hI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761836449; c=relaxed/simple; bh=Ew9bDOfsGNCkgMqmB9MukJ7vGVG4zknpNWCN+C4T1jc=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=atxZvKIu7X3BCBKO8n6zt9AswbsIXeEz6idMqp6reIKvK8ISYx/dMBdMwqa+mmyXSI0X7OrwUL5u9wiFEu0dWSK6Crl2gM6rTK8KTYXod/lrXY9xY8YtwLcWJilwuSDV5DCe+SIjohJuHfhyqDWm3T4bzIC1XopqlilicQ1L1Wc= 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=abERtiOk; arc=none smtp.client-ip=192.198.163.18 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="abERtiOk" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1761836447; x=1793372447; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=Ew9bDOfsGNCkgMqmB9MukJ7vGVG4zknpNWCN+C4T1jc=; b=abERtiOk91AlZacT5r3ZQtc3UyP1ql/g6kk9/4SsKpl9TAbx/MRxM5id 0wtXjzcKg8XeIggYAeqIwMYoiP1eKHRtJ85T31KRkcOmnQkzQMJty6UxJ orTRqHJZP5TDTUkrdHVkETkBtPVyOH8lgpxW1ag9E0zQQg3YBkBc7240F ++N93LP/WTsGkXYAT1wmxv2+3I9FXz2BMFLn5W4ukCFiiXs2AOH2xR9j5 L01lmUqemnl6BksArQzmCePDj+hM+9XQWSk+QLrAyGcLHgHWqCDWPn8vl W0qaA/2o5z7VBuKLnPgItD5d95odAhCTil1SUGzae1svCbyvgQuxUGObr Q==; X-CSE-ConnectionGUID: hoVatYODTiS4cvDOXE/IPw== X-CSE-MsgGUID: MIShqGT8SK6cg7YJ4G8Qzw== X-IronPort-AV: E=McAfee;i="6800,10657,11598"; a="63184807" X-IronPort-AV: E=Sophos;i="6.19,267,1754982000"; d="scan'208";a="63184807" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by fmvoesa112.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Oct 2025 08:00:47 -0700 X-CSE-ConnectionGUID: Lf1QQcWxQp+W9ot4o8jNNw== X-CSE-MsgGUID: q101Fl31SBGpSZcJpUWkjg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.19,267,1754982000"; d="scan'208";a="186418599" Received: from aschofie-mobl2.amr.corp.intel.com (HELO [10.125.109.249]) ([10.125.109.249]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Oct 2025 08:00:47 -0700 Message-ID: Date: Thu, 30 Oct 2025 08:00:46 -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: x86/fpu: Inaccurate AVX-512 Usage Tracking via arch_status To: chuang Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , open list References: 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 10/29/25 23:56, chuang wrote: ... > I traced the code path within fpu_clone(): In fpu_clone() -> > save_fpregs_to_fpstate(), since my current Intel CPU supports XSAVE, > the call to os_xsave() results in the XFEATURE_Hi16_ZMM bit being > set/enabled in xsave.header.xfeatures. This then causes > update_avx_timestamp() to update fpu->avx512_timestamp. The same flow > occurs in __switch_to() -> switch_fpu_prepare(). So that points more in the direction of the AVX-512 not getting initialized. fpu_flush_thread() either isn't getting called or isn't doing its job at execve(). *Or*, there's something subtle in your test case that's causing AVX-512 to get tracked as non-init after execve(). > Given this, is the issue related to my specific Intel Xeon Gold? Is > the CPU continuously indicating that the AVX-512 state is in use? As much as I love to blame the hardware, I don't think we're quite there yet. We've literally had software bugs in the past that had this exact same behavior: AVX-512 state was tracked as non-init when it was never used. Any chance you could figure out where you first see XFEATURE_Hi16_ZMM in xfeatures? The tracepoints in here might help: /sys/kernel/debug/tracing/events/x86_fpu Is there any rhyme or reason for which tasks see avx512_timestamp getting set? Is it just your test program? Or other random tasks on the system?