From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0a-002e3701.pphosted.com (mx0a-002e3701.pphosted.com [148.163.147.86]) (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 7145025B08D for ; Fri, 22 May 2026 02:09:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.147.86 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779415787; cv=none; b=bVPX16L9qt6x1Rcv2yNnNuWASN6kXn9WyGycrUn8STonfI9g/TeLdSnZKA5+fb4XgT/+DmWcBysBqGigR8sA6Au6a+HWZHiRSyL1MyfmIznRV8QKmOGNMyGAJ9caprhIlsJM7SqnJFjWgRK2LCX+5BpxlzJ6NmR9+DRh2yod05E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779415787; c=relaxed/simple; bh=THui63zubHcr7qpf6np3MXeuREahTCfyllT77+/pboc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=kVcrC848chWP9oPgdw77O3+4cjick0QtbZkYD5wLD7kfg8hAwR6Eo0OCBVAPUFPTMtM3HxVy4A1NTFnHZBxNm32mxdkKuWijF+/X1kOFg3MF7mNHVWfSWF2V3XSV5Z83fzwEaJFCQyjBOG+vNtzF9xjv9AhNlwpsFpgaw8V+rGI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=hpe.com; spf=pass smtp.mailfrom=hpe.com; dkim=pass (2048-bit key) header.d=hpe.com header.i=@hpe.com header.b=foz9QbLa; arc=none smtp.client-ip=148.163.147.86 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=hpe.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=hpe.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=hpe.com header.i=@hpe.com header.b="foz9QbLa" Received: from pps.filterd (m0150241.ppops.net [127.0.0.1]) by mx0a-002e3701.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 64M1FNlB4191611; Fri, 22 May 2026 02:08:50 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=hpe.com; h=cc :content-type:date:from:in-reply-to:message-id:mime-version :references:subject:to; s=pps0720; bh=rMHgNAH4+28ooX0CAv4W+KivA6 PShs/OXEWMkIb+Zi0=; b=foz9QbLaA1vadbYRw7PI27qB29MrkzOsQi3Nmlnho3 F2Z6hUL9j+LQT67pqjpBwfuOQmGNOAYprWLMfusR5Tp1mvEYSUgl7YdFbp7ZQJEH q/3p1RQ0AcT5pqtfCzGT30FwdKguwkyFVFNHdP99Lyos/+QRoX7aA4tS1vWoS0Vr vkH/cWKICg/6KQKpaMBYKNk6oufrni9T2QOegBJs42eMpOnkmzNjrDQTngbb9Fj6 P6lFRo8LXoypuC61EZhCuXZ96JoEJXWIBwjFRYOv8CdN13Nfgjin1BvwDn9vUvH4 VgOa/9TzWVvjTiccU9gPMLu6HJO+xrQ01bAfQboh0xww== Received: from p1lg14879.it.hpe.com (p1lg14879.it.hpe.com [16.230.97.200]) by mx0a-002e3701.pphosted.com (PPS) with ESMTPS id 4eadaergem-1 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Fri, 22 May 2026 02:08:50 +0000 (GMT) Received: from p1lg14885.dc01.its.hpecorp.net (unknown [10.119.18.236]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by p1lg14879.it.hpe.com (Postfix) with ESMTPS id E9CCC1314F; Fri, 22 May 2026 02:08:38 +0000 (UTC) Received: from hpe.com (unknown [16.231.227.39]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (Client did not present a certificate) by p1lg14885.dc01.its.hpecorp.net (Postfix) with ESMTPS id 1E5268005CB; Fri, 22 May 2026 02:08:35 +0000 (UTC) Date: Thu, 21 May 2026 21:08:34 -0500 From: Dimitri Sivanich To: Thomas Gleixner Cc: Linux Kernel Mailing List , Jiri Wiesner , Steve Wahl , Justin Ernst , Kyle Meyer , Russ Anderson , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , "Peter Zijlstra (Intel)" , Ilpo =?iso-8859-1?Q?J=E4rvinen?= , Marco Elver , "Guilherme G. Piccoli" , Nikunj A Dadhania , "Xin Li (Intel)" , Dimitri Sivanich Subject: Re: [PATCH v4 0/2] x86/tsc: Exempt recent UV systems from clocksource watchdog checks to avoid false positives. Message-ID: References: <87lddcv9vd.ffs@tglx> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87lddcv9vd.ffs@tglx> X-Proofpoint-ORIG-GUID: yUGZVZ0a_RnWUpbNnkUIlzkMBgPhMvDS X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTIyMDAxOSBTYWx0ZWRfX4TdWF94GLG35 tBpmbWI8LSvopLIQb+mjWhg0fuq1/qmEoGhehuZ75pLenVCpqzIDcbEoy5TmB5kOk0D4yK+AsDt 4yz3/Hw9iT5rYjt3zYz3rtjO/o1gpgH9rwhB43m4p72ktfwJGqbBgVNQwP/hSzmkK96jDQut29d i7QqW3WjClpPxaKt2ieyU1pVGzFCpGfKmonq4yCr/zQxV8w1jy+NrLXGs4iw/9VFehu1Zo8swxZ 16iHV85yXRrFhp4ua0padaFsVLIZJfCuMgQ0p75x6MMI3tlgxAD2O6vCjaYwG+liklJ6er1i8ZM G3O8yT5tLAXSjVFcbp+FpSEK+nW5PZwjEKX/lKpVRyjftFvneZZHtigtzFzJdtGSt93tqza88Kp FY9x5e7stl4fvdRjTc/c5/LKzxI0tXgWUihrY6GQVcZh8ZlyOWgRDO16o/fwU/kE5vC/nnPzDoV pvB6kzsmqL1arPbIWNQ== X-Authority-Analysis: v=2.4 cv=c5Gbhx9l c=1 sm=1 tr=0 ts=6a0fbab2 cx=c_pps a=5jkVtQsCUlC8zk5UhkBgHg==:117 a=5jkVtQsCUlC8zk5UhkBgHg==:17 a=kj9zAlcOel0A:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=gQcMVamqm3wCPoSYhaRC:22 a=_ZmgHqWwjZUDpi_pur5s:22 a=VQemR7Wtkf-WFJKPaS4A:9 a=CjuIK1q_8ugA:10 X-Proofpoint-GUID: yUGZVZ0a_RnWUpbNnkUIlzkMBgPhMvDS X-HPE-SCL: -1 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-21_05,2026-05-18_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 priorityscore=1501 spamscore=0 phishscore=0 lowpriorityscore=0 adultscore=0 suspectscore=0 malwarescore=0 impostorscore=0 bulkscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605130000 definitions=main-2605220019 On Thu, May 21, 2026 at 09:30:14PM +0200, Thomas Gleixner wrote: > On Thu, May 21 2026 at 08:17, Dimitri Sivanich wrote: > > HPE UV hardware and firmware is designed to ensure a reliable and > > synchronized TSC mechanism. Comparing the TSC against secondary > > clocksources can result in false positives due to variable access > > latency caused by system traffic. The best course of action against > > these false positives has been found to simply disable watchdog > > checking of the TSC. > > > > Commits [1] and [2] were introduced to avoid an issue where the TSC > > is falsely declared unstable by exempting qualified platforms of up > > to 4-sockets from TSC clocksource watchdog checking. Extend that > > exemption to include recent and future UV platforms. > > Jiri asked you in the V3 submission: > > "A new implementation of the clocksource watchdog has been merged into > the upstream kernel. One of the changes made by the new clocksource > watchdog implementation is that reference clocksource reads are made > on the boot CPU only. Perhaps, the sgi_rtc clocksource would work well > with this implementation. So, testing is needed in order to find out > if this patch are any future in the upstream Linux. Dimitri, would you > be able to run tests on UV systems to check if the new clocksource > watchdog implementation works and the hardware limitations of sgi_rtc > do not get in the way?" > > This question is still not answered by you and it has been confirmed > that the new watchdog works flawlessly on a 1920 threads 16 socket > system under massive load and system traffic. I tested a 7.1-rc4 kernel on a 2048 thread 16 socket system and, while under test, the TSC did get marked as unstable after a series of "sgi_rtc read timed out" warnings. > > So you do not even have the courtesy to test, you just go and make the > same claims you made before based on the original watchdog > implementation. > > Feel free to ignore people, but then don't be surprised when people > ignore you as well. > > Thanks, > > tglx