From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0b-002e3701.pphosted.com (mx0b-002e3701.pphosted.com [148.163.143.35]) (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 C7CB2370D63 for ; Tue, 19 May 2026 20:04:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.143.35 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779221097; cv=none; b=CIiuQOZduuvHP9bremFAAtrWOpDjPFK4hQKvEyH3typoYtdVaUxDg5vaOgbW3y5YLujYKdTob/uEfs0PUMMERYDYy9Kulyy2cP9UIf+YioHyrcvYWkwpKv+cDAMP2IH9eTeQPaUuPaflmOpD9GdSjxBSeC/jOSomYuaUrEQJvus= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779221097; c=relaxed/simple; bh=bAtV6kI3oOpaQP2/Axu6j77SX+TkE4mD7UKesLiUJOc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tzSnOucLS0+vDA0HvONku2fpHy4jtTdlwreuQ7tUdaopSwC5K7jMffm7L8XhrJvPkNBaIk7T0cHb0sa0ONeGJEC4ISuzYH7J8cDQJ69IDMH7h5HxCoah/Eeic6mAHW+fGdbXSvKdqx3Xtspah8P3Fw4RIKFcuErcn5h0eVN1hW0= 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=lU5le/Mq; arc=none smtp.client-ip=148.163.143.35 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="lU5le/Mq" Received: from pps.filterd (m0134424.ppops.net [127.0.0.1]) by mx0b-002e3701.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 64JK3NGN219233; Tue, 19 May 2026 20:03:54 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=v3AohJgTsF2Bf9VxumerRh+N2p KqiKc6eTyETBuPrto=; b=lU5le/Mq9/DPnWwgaUk2u83q2tcHSXGfGPCY5csq4m nWYGnLo69AGJrA8MNxjTH9hfakbjw0VJOgrFTjdlBCdsz/qcf9M65fq9ryrSLi5/ fDRAL+3K3UyYUhFD/8dO3M1oV2fnsZnQ0zoJRPgCK9LZ/Hyxzmp3+uPy+WZGIIcH nDqtqZjXSAdUfZVJz0aFn3BCluphxk6j+gnIPYwwUqEpIF+gSWjHpQRNuE62gX3d HInVaDy/XhjFlbuLqJWfwn+dvV07v7wIk0Ce/SCqrpIWw/QrwceozaWWVbXnlhVX LncxHknm/GFrPqNxBEQPLMt0wkXmy7q9FvCjZBPlzY6g== Received: from p1lg14880.it.hpe.com (p1lg14880.it.hpe.com [16.230.97.201]) by mx0b-002e3701.pphosted.com (PPS) with ESMTPS id 4e8qdjy8qh-1 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Tue, 19 May 2026 20:03:53 +0000 (GMT) Received: from p1lg14886.dc01.its.hpecorp.net (unknown [10.119.18.237]) (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 p1lg14880.it.hpe.com (Postfix) with ESMTPS id 32DF381B851; Tue, 19 May 2026 20:03:46 +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 p1lg14886.dc01.its.hpecorp.net (Postfix) with ESMTPS id EAF52810CDD; Tue, 19 May 2026 20:03:41 +0000 (UTC) Date: Tue, 19 May 2026 15:03:39 -0500 From: Dimitri Sivanich To: Jiri Wiesner Cc: Linux Kernel Mailing List , Steve Wahl , Justin Ernst , Kyle Meyer , Russ Anderson , Thomas Gleixner , 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 v3] x86/tsc: Disable clocksource watchdog for TSC on recent UV Message-ID: References: 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: X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTE5MDIwMCBTYWx0ZWRfXygg6ZcrN/jo2 Ey4iEXcNbFW3yUhqAWjj2O4xkGNCW7zob6i3/nRpv8L/CJkw7dAo7hJc5ci1zsXKrBXjE4ZSp1e xAqSEhpK+ilSby+8aCXoek6XZhz9pnD9Gv7rKuHEGYxEvNX1D2hT6wD2g4halhsLnN4Gf3sCIP1 +0D4svFihhtaMAYzDLDKOyj/abIr0fTz6ddEJH2S+f8jzo7jjNjicr7Wezi+NSPzRYyQiFjydsR 79l9H50SelU1anbrIw4k3EqqBPdnxm6/F3G3Nt3r1V37Ut30FqvSKOfoy0i6o/sYWCXvTqTyxg4 oR9HT98tAT5KzXUW7ilcobwT5icXPEWI9HdFTt5ccgJ/wfJPdkslllvKW2NCAFpIzVyfyu0ZKjA d0Uaf6dSimvWvzwCOtl+F/FIzCQ1iCakIzl4Dasx7t91xboTJPBVB1jvkusH7JgQ5ndL4/agciY Vt6ATYxwVaQesNTX6yg== X-Proofpoint-ORIG-GUID: zozB0v0g3sNbaL0rvG0qOO47gt_-uMdJ X-Proofpoint-GUID: zozB0v0g3sNbaL0rvG0qOO47gt_-uMdJ X-Authority-Analysis: v=2.4 cv=ON4XGyaB c=1 sm=1 tr=0 ts=6a0cc229 cx=c_pps a=A+SOMQ4XYIH4HgQ50p3F5Q==:117 a=A+SOMQ4XYIH4HgQ50p3F5Q==:17 a=kj9zAlcOel0A:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=gQcMVamqm3wCPoSYhaRC:22 a=3haJ9R1Aw3gUfsUHDaCR:22 a=zIvIbtpzcMm00Kuj3AMA:9 a=CjuIK1q_8ugA:10 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=2026-05-19_05,2026-05-18_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 bulkscore=0 malwarescore=0 lowpriorityscore=0 adultscore=0 suspectscore=0 spamscore=0 clxscore=1011 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605130000 definitions=main-2605190200 On Thu, May 14, 2026 at 09:53:31AM +0200, Jiri Wiesner wrote: > Hello, > > On Tue, Oct 07, 2025 at 11:32:17AM -0500, Dimitri Sivanich wrote: > > Disable clocksource watchdog checking on recent and future UV platforms > > to avoid false positives. > > > > Commits 'b50db7095fe0 ("x86/tsc: Disable clocksource watchdog for TSC on > > qualified platforms")' and '233756a640be ("Extend watchdog check exemption > > to 4-Sockets platform")' 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. > > I am sorry for being MIA for all this time. Apart from HPE customers who do not follow the instruction to add tsc=nowatchdog to the kernel command line, there is another use case for this patch. It has to do with SUSE's efforts to ship a single image per product for deploying machines in the cloud. HPE UV systems that will be used as bare metal are one of the planned instances. The old implementation of the clocksource watchdog needs to be switched off on those UV systems. So, the intention is to backport this patch to all SLES releases that are in active use in the cloud. > > 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? Jiri, I'll be submitting a V4 patch to address this.