From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3C216C433F5 for ; Fri, 17 Sep 2021 09:36:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2334C60F93 for ; Fri, 17 Sep 2021 09:36:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241089AbhIQJhx (ORCPT ); Fri, 17 Sep 2021 05:37:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53426 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241256AbhIQJhu (ORCPT ); Fri, 17 Sep 2021 05:37:50 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6CBE7C061764; Fri, 17 Sep 2021 02:36:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=p4JKQZLvY28YAWtmOrT5h9vdEtIffVYjwaqM8dQlSuk=; b=QQ1aRlrpBKnxNb39uc5Qg3Q7Mr mtZkjFZ5HTcmaUZIpBhEXzPz8Jnq6weWSkgUpL2ZOUKilOgIzFGCCQ2JsASe/UWeepzzTAjnuDSq/ d6jWrwALsAtBH8rcEhZ+gYCxsXuVXFUGJOMOaY7EEWS0badAoBtcsot+9NjjB9RUWHxdKrXSpyoWO SsUpBM5dYmSkstVKdjvPRDnp/KwGbaSrzJz1ye5fIQ+BmZREMveigINbT/jf2nETmaC4DVkZTgQty TBmtDdFa01zzoYOtyQRMOP/09HS+XUE9of6QOoTBGDhK6xQ/sDImSguyhQk0jy0WfDEywITFiV7p3 fsnyYQIg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1mRAGX-00070u-2K; Fri, 17 Sep 2021 09:34:59 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 1C000300260; Fri, 17 Sep 2021 11:34:40 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id EF47A2083B0E0; Fri, 17 Sep 2021 11:34:39 +0200 (CEST) Date: Fri, 17 Sep 2021 11:34:39 +0200 From: Peter Zijlstra To: Bjorn Helgaas Cc: Jakub Kicinski , x86@kernel.org, jose.souza@intel.com, hpa@zytor.com, bp@alien8.de, mingo@redhat.com, tglx@linutronix.de, kai.heng.feng@canonical.com, bhelgaas@google.com, linux-pci@vger.kernel.org, rudolph@fb.com, xapienz@fb.com, bmilton@fb.com, stable@vger.kernel.org Subject: Re: [PATCH] x86/intel: Disable HPET on another Intel Coffee Lake platform Message-ID: References: <20210916131739.1260552-1-kuba@kernel.org> <20210916150707.GA1611532@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Fri, Sep 17, 2021 at 11:11:49AM +0200, Peter Zijlstra wrote: > On Thu, Sep 16, 2021 at 10:07:07AM -0500, Bjorn Helgaas wrote: > > This seems to be an ongoing issue, not just a point defect in a single > > product, and I really hate the onesy-twosy nature of this. Is there > > really no way to detect this issue automatically or fix whatever Linux > > bug makes us trip over this? I am no clock expert, so I have > > absolutely no idea whether this is possible. > > X86 is gifted with the grant total of _0_ reliable clocks. Given no > accurate time, it is impossible to tell which one of them is broken > worst. Although I suppose we could attempt to synchronize against the > PMU or MPERF.. > > We could possibly disable the tsc watchdog for > X86_FEATURE_TSC_KNOWN_FREQ && X86_FEATURE_TSC_ADJUST I suppose. > > And then have people with 'creative' BIOS get to keep the pieces. Alternatively, we can change what the TSC watchdog does for X86_FEATURE_TSC_ADJUST machines. Instead of checking time against HPET it can check if TSC_ADJUST changes. That should make it more resillient vs HPET time itself being off.