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=-3.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE, 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 6776EC12002 for ; Sat, 17 Jul 2021 00:24:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 479DE613D0 for ; Sat, 17 Jul 2021 00:24:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229756AbhGQA1r (ORCPT ); Fri, 16 Jul 2021 20:27:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35664 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229462AbhGQA1q (ORCPT ); Fri, 16 Jul 2021 20:27:46 -0400 Received: from mail-pg1-x530.google.com (mail-pg1-x530.google.com [IPv6:2607:f8b0:4864:20::530]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BB2D7C06175F for ; Fri, 16 Jul 2021 17:24:50 -0700 (PDT) Received: by mail-pg1-x530.google.com with SMTP id k20so11578043pgg.7 for ; Fri, 16 Jul 2021 17:24:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=kapKSccYf+3d8IEDbRUj0u/6LBJIHmDYeekKIvB07CM=; b=QuPsbhLsvtd9XpYR91VosjMB3PPm7XoKqQ6bSM7zU6K4f+gIZy2K1PS2oodCR/B18p Yz6wCLfZGeHBy1z9kRR9G4wgFRm7d61JzEsZHA+6wgD25K6Ly2FKbrd01HXNCL4U6hcb 7bIR+OqDG2FMe7TiHbP0UfPrSbNY6zOaXWZa0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=kapKSccYf+3d8IEDbRUj0u/6LBJIHmDYeekKIvB07CM=; b=F5CAHG7aOnqSZIzJXqSpdoe6B7XZZA2Ii7rCB1wgxjpwca03bYKDKAM3LcBosoXkS/ 5YacFNla+WmHwNd1aptpVqKopF5kY7IHOa4vqYfC2JRbVHp4SyOVf4TNWndJGE/TJuOW 13QJhUwKY0msnlbrntOQ6Uf57AcXAa/yJON/UqAv9hZWP0FG8qxy9Cmw/sRTvxCf/Zy2 MdkQaJZhQPZELOtpYquxAVnwmInB5g/8OdBgUExV5yil1GAM3T/jl0IrvytvBZlQ8Zr8 k64aqmCrwvCs+YRybQkLmEm9obfbF6iF+vwO1Qsx95J3vWWnOlA92iZoMnptrqQxp5Ec BPkQ== X-Gm-Message-State: AOAM532cuz31ih6dghiXI46Pefw3x0izOXYQ+x/hlzcQsTHR3lKdWbfK r56F3ysV8aUPJ9IaSQdqVIIYaw== X-Google-Smtp-Source: ABdhPJzaA08Bg4H8f+oxijbl0pXZESDDUpg8+o2qUI2cA0P+MmccR8kd9Gy5hbpsXo1yaCaxLOIyHQ== X-Received: by 2002:a63:d014:: with SMTP id z20mr12457261pgf.203.1626481490358; Fri, 16 Jul 2021 17:24:50 -0700 (PDT) Received: from google.com ([2409:10:2e40:5100:9be5:9410:eeb8:524e]) by smtp.gmail.com with ESMTPSA id o25sm12819698pgd.21.2021.07.16.17.24.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Jul 2021 17:24:49 -0700 (PDT) Date: Sat, 17 Jul 2021 09:24:43 +0900 From: Sergey Senozhatsky To: Sergey Senozhatsky Cc: Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Suleiman Souhlal , "Paul E . McKenney" , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] x86/kvm: do not touch watchdogs in pvclock Message-ID: References: <20210716053405.1243239-1-senozhatsky@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210716053405.1243239-1-senozhatsky@chromium.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (21/07/16 14:34), Sergey Senozhatsky wrote: > > > apic_timer_interrupt() > smp_apic_timer_interrupt() > hrtimer_interrupt() > _raw_spin_lock_irqsave() > lock_acquire() > __lock_acquire() > sched_clock_cpu() > sched_clock() > kvm_sched_clock_read() > kvm_clock_read() > pvclock_clocksource_read() > pvclock_touch_watchdogs() > > Since this is VM and VCPU resume path, jiffies still maybe > be outdated here, which is often the case on my device. > pvclock_clocksource_read() clears PVCLOCK_GUEST_STOPPED, > touches watchdogs, but it uses stale jiffies: 4294740764 > (for example). Hmm, on the other hand, there is probably nothing that guarantees that the first watchdog hard IRQ we execute on a resuming VCPU is going to see updated jiffies, it still can use stale jiffies.