From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.14]) (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 769D558FD22 for ; Wed, 16 Sep 2026 23:13:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.14 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789600439; cv=none; b=rVe3Ut+haFqU6ciCW0xD3uJVmNfJ26ws9zU1TpxQudC9QkyBY0yuD6lfCwbhICTbPFb5JeVs7uj3usy1W05BqS8fcdmkHALkUTxE7H2lY9c+XaUtIuSLAQAoXEaNkdNrpIm6XBuzJDmYwextLoFyKLqBDpk58eRARPA7v7TreYI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789600439; c=relaxed/simple; bh=ydpynI7FWRcDuv3jJBE/xxqcbkyClGw2KGJIvYL2PfA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=V6Qsb09yvGnp3G9K4YkS2BfKPMrWgIyMmxjkWtic8U7UduHJ+X7aGSD9N2rXcq39hR13tgaaYBMjQkd0CiOhSzFpUMMdnsje4kzdh537VtwfZuBVUWjMDnw6hh1m0w44eGj0oHsRAco5+LKBxdpXxfDMUTDh6ylZthShx/H8uY8= 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=PfrSFRfF; arc=none smtp.client-ip=198.175.65.14 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="PfrSFRfF" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1789600438; x=1821136438; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=ydpynI7FWRcDuv3jJBE/xxqcbkyClGw2KGJIvYL2PfA=; b=PfrSFRfFal9U9CTQ8dtC9C++Vbyz3hnG+BXUpx6+yWj77zwradePgf1N TPR4IJWw6S/blc0KX+ZS9m7eVWY0oUO5A8a+PsPhEFHLGf5lUQg1c6Su3 3trcpuZTYN1SF2oBh6PuGyw5l9RG9LibajUy/WAUyMmG7D3dsEvKEaQc0 OkCDWGqHc6XS33a0t/HppAzEplJ9K6XTqXByXWyv2nQFmYGt9fuxlYrAd xS8nh1VDkdhSgmziqZkG6s5az1NE0z8CLPC+70E0KWeSloIrZhsQX9Y3j s4XxiihUNAfY7w7YMMGb6TW6ZkTOgI0Xiyk9sHX+gL6SceYfbqFaTtFZn w==; X-CSE-ConnectionGUID: dxJyyyBCRY2yQm9HetLoRw== X-CSE-MsgGUID: iPU3cyivQzOCPnCaGW1aEQ== X-IronPort-AV: E=McAfee;i="6800,10657,11905"; a="93861549" X-IronPort-AV: E=Sophos;i="6.27,103,1787036400"; d="scan'208";a="93861549" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by orvoesa106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Sep 2026 16:13:41 -0700 X-CSE-ConnectionGUID: 6uAJXPrqTSOky6uUNq5jBA== X-CSE-MsgGUID: sJ7fYBpYSqqIeQApm81J5w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,103,1787036400"; d="scan'208";a="277231511" Received: from khuang2-desk.gar.corp.intel.com (HELO agluck-desk3.home.arpa) ([10.124.223.219]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Sep 2026 16:13:41 -0700 From: Tony Luck To: Fenghua Yu , Reinette Chatre , Maciej Wieczor-Retman , Peter Newman , James Morse , Babu Moger , Drew Fustini , Dave Martin , Chen Yu , David E Box , x86@kernel.org Cc: Christoph Hellwig , linux-kernel@vger.kernel.org, patches@lists.linux.dev, Tony Luck Subject: [PATCH v12 25/25] x86,fs/resctrl: Document telemetry mount timing caveat Date: Wed, 16 Sep 2026 16:13:20 -0700 Message-ID: <20260916231320.14502-26-tony.luck@intel.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260916231320.14502-1-tony.luck@intel.com> References: <20260916231320.14502-1-tony.luck@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The PMT driver enumerates telemetry features asynchronously, so an automatic mount of resctrl from /etc/fstab early in boot may occur before those features are available, resulting in them not being enabled in the mounted instance. Add a footnote to the 'If telemetry monitoring is enabled' sentence pointing readers to a new "Mounting resctrl with telemetry" section. That section explains the race. Signed-off-by: Tony Luck --- v12: Drop problematic examples of systemd/udev rules. --- Documentation/filesystems/resctrl.rst | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst index e4b66af55ffb..91a2ab0fa027 100644 --- a/Documentation/filesystems/resctrl.rst +++ b/Documentation/filesystems/resctrl.rst @@ -630,7 +630,7 @@ When monitoring is enabled all MON groups will also contain: each instance of an L3 cache. Each directory contains files for the enabled L3 events (e.g. "llc_occupancy", "mbm_total_bytes", and "mbm_local_bytes"). - If telemetry monitoring is enabled, there will be a "mon_PERF_PKG_YY" + If telemetry monitoring is enabled [#]_, there will be a "mon_PERF_PKG_YY" directory for each physical processor package. Each directory contains files for the enabled telemetry events (e.g. "core_energy". "activity", "uops_retired", etc.) @@ -669,6 +669,10 @@ When monitoring is enabled all MON groups will also contain: returned if the MBM event does not have an assigned counter in the CTRL_MON group nor in any of its associated MON groups. +.. [#] Telemetry features are enumerated asynchronously by the PMT driver, so + an automatic mount of resctrl from ``/etc/fstab`` at boot may not enable + them. See `Mounting resctrl with telemetry`_ below. + "mon_hw_id": Available only with debug option. The identifier used by hardware for the monitor group. On x86 this is the RMID. @@ -1898,6 +1902,18 @@ m. Unmount the resctrl filesystem. # umount /sys/fs/resctrl/ +Mounting resctrl with telemetry +=============================== + +Telemetry features (e.g. the ``mon_PERF_PKG_YY`` events) are enumerated +asynchronously by the PMT driver. If resctrl is mounted before that +enumeration completes (for example, when mounted automatically from +``/etc/fstab`` early in boot) the telemetry features will not be available +at mount time and will therefore not be enabled in the mounted instance. + +To avoid this race, defer the mount until after the ``pmt_telemetry`` module +has loaded. + Intel RDT Errata ================ -- 2.55.0