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=-0.5 required=3.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 249D5C433ED for ; Wed, 7 Apr 2021 11:02:50 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A5D77611EE for ; Wed, 7 Apr 2021 11:02:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A5D77611EE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:59976 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lU5xQ-00055i-Mu for qemu-devel@archiver.kernel.org; Wed, 07 Apr 2021 07:02:48 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33146) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lU5wn-0004Va-84 for qemu-devel@nongnu.org; Wed, 07 Apr 2021 07:02:09 -0400 Received: from mail-ot1-x32c.google.com ([2607:f8b0:4864:20::32c]:43629) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1lU5wf-000193-KK for qemu-devel@nongnu.org; Wed, 07 Apr 2021 07:02:08 -0400 Received: by mail-ot1-x32c.google.com with SMTP id s16-20020a0568301490b02901b83efc84a0so8719027otq.10 for ; Wed, 07 Apr 2021 04:01:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=za16kTG1cVGjMQbsKKT5zr6PyamPPMULoUa4ewYf/WA=; b=WjBDyd/4lguKJH2X+BNdfyWBLsK9hy6P4h/Tt7J0SZliOb/024sh1+ENobxY+/Odwh /Lk4m1xFkNfFYCTLGQURv0xuI2hjzX40yg5GrYASEvq8Uqab98l/NQaXwfLde9bD2RQT 6iwU6MyBrikYCZjsh0jOu1nu4iWRMp68KZ2btnyvuKcHqeedo9DUxPk9B5tZlCQFaV5u S0Y/4gBa7NcwHP1tLQilvpa4pHXMMbC4PgP1VTjjaH8wdgUZrUKqsqbD0kiSwo1Wsi5G ygvM4n1gywPl5VMN4DVM6KsMwM1VUUf3DmfObkuHYrHSL5aIM03v8D2KrrIh4YmjHmUZ kCeQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=za16kTG1cVGjMQbsKKT5zr6PyamPPMULoUa4ewYf/WA=; b=W7LYRC/CDunC7tLGwI84U+t60IPgscXqfDCLHOc9u/0lpzCcifjOS3bgcHmbWgXCLK eDw2GJZO7YaywZ7MR8I0NGJvvMSPUnPX6oU4xUo+82Y5E9tNlSK+X1t+vRZqryXqNUHF gr7pb9R5NH3dmTMP3qLEmJlpLaOJL0MGPqqHaWqx+5oT8ikyauf/vUrbY0UzA2HW65XL Tn5LtVED9WGZ8Kx9uVpebhuM/yhuCL1HV1NQk26Ka7jTLI4o67y3UMjSztLgzBUPYWqT IjUOBsyAo3kCXMrbZrpoSrqIA+uamUwHZcl64IAJ5LSqSz8nmGSZbHNWbS22qFOqvalL YIdg== X-Gm-Message-State: AOAM532rI+MnIlH1/14sGEO7dMTIpHkdHMfzVqLpDKXjymPtk3hlTP4g 9gejCKdwIYiKsqNwHpt47iH0XUkrB0pEelLfDWA= X-Google-Smtp-Source: ABdhPJx/DhF9inZq1zuvLn8Ya8I1W+rN/Gz4wclBP73yCJTIou0M8QZIK0Yw84E71ASVqXZPhPdaR0XEyN1OOmflb0c= X-Received: by 2002:a9d:6b13:: with SMTP id g19mr2441704otp.185.1617793314695; Wed, 07 Apr 2021 04:01:54 -0700 (PDT) MIME-Version: 1.0 References: <36088364-0b3d-d492-0aa4-59ea8f1d1632@msgid.tls.msk.ru> In-Reply-To: <36088364-0b3d-d492-0aa4-59ea8f1d1632@msgid.tls.msk.ru> From: Wanpeng Li Date: Wed, 7 Apr 2021 19:01:42 +0800 Message-ID: Subject: Re: Commit "x86/kvm: Move context tracking where it belongs" broke guest time accounting To: mjt@tls.msk.ru Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=2607:f8b0:4864:20::32c; envelope-from=kernellwp@gmail.com; helo=mail-ot1-x32c.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , Thomas Gleixner , "qemu-devel@nongnu.org Developers" , kvm Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, 7 Apr 2021 at 18:55, Michael Tokarev wrote: > > Hi! > > It looks like this commit: > > commit 87fa7f3e98a1310ef1ac1900e7ee7f9610a038bc > Author: Thomas Gleixner > Date: Wed Jul 8 21:51:54 2020 +0200 > > x86/kvm: Move context tracking where it belongs > > Context tracking for KVM happens way too early in the vcpu_run() > code. Anything after guest_enter_irqoff() and before guest_exit_irqoff() > cannot use RCU and should also be not instrumented. > > The current way of doing this covers way too much code. Move it closer to > the actual vmenter/exit code. > > broke kvm guest cpu time accounting - after this commit, when running > qemu-system-x86_64 -enable-kvm, the guest time (in /proc/stat and > elsewhere) is always 0. > > I dunno why it happened, but it happened, and all kernels after 5.9 > are affected by this. > > This commit is found in a (painful) git bisect between kernel 5.8 and 5.10. Thanks for the report. I have a patch here which can fix it. https://lore.kernel.org/kvm/1617011036-11734-1-git-send-email-wanpengli@tencent.com/ Wanpeng