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 6A948C4361B for ; Tue, 15 Dec 2020 22:35:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3CD3E22CB8 for ; Tue, 15 Dec 2020 22:35:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729963AbgLOWfp (ORCPT ); Tue, 15 Dec 2020 17:35:45 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:35416 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727068AbgLOWfc (ORCPT ); Tue, 15 Dec 2020 17:35:32 -0500 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1608071687; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=AodAqwSxT8qVb0KNVb01jp7kOxVR15QYTpc+MfSTHL8=; b=nk8VxAGN4PWz+BZskR1A7Ox9M88LfWpTvQWvEPGbIR3e9QpAkHchvLHzTskPnzzCRwPm7J VSKPwzdwmkABT8U6CFK18RmwXjRPIRS+FK8Wvqb0tmzRjU+cGXOoUdSRPUqEztcrFRsMHK yOvLBc+okyF+4Lm6Shyr04IBSmLzrLU4KAi3v6xYNYG1TUOv+zutwS8xDLSgz8+d/Pfl3S VEalFA2RgvrGIa1gYOqMREPl6f+bPfOfAQOGCd5Y+b90FjfoMVNijAFIUE6QdmDodiG9QE KSN7/xLQEOsXElnUhWGZFzVxCbpHtyBVqzMKmHXpmkF1QY6QUuJ9SDEioNOMfg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1608071687; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=AodAqwSxT8qVb0KNVb01jp7kOxVR15QYTpc+MfSTHL8=; b=1rEbFhcEjnOMCATHobfWvWljuRdE7JwGMfjuCVGsmjXXD7enxnAJLHm2POzi+c7JPQLhM+ mpYzmpNZp1Ti6LDg== To: Marcelo Tosatti , Paolo Bonzini Cc: Maxim Levitsky , kvm@vger.kernel.org, "H. Peter Anvin" , Jonathan Corbet , Jim Mattson , Wanpeng Li , "open list\:KERNEL SELFTEST FRAMEWORK" , Vitaly Kuznetsov , Sean Christopherson , open list , Ingo Molnar , "maintainer\:X86 ARCHITECTURE \(32-BIT AND 64-BIT\)" , Joerg Roedel , Borislav Petkov , Shuah Khan , Andrew Jones , Oliver Upton , "open list\:DOCUMENTATION" Subject: Re: [PATCH v2 1/3] KVM: x86: implement KVM_{GET|SET}_TSC_STATE In-Reply-To: <20201215105927.GA3321@fuller.cnet> References: <875z5c2db8.fsf@nanos.tec.linutronix.de> <20201209163434.GA22851@fuller.cnet> <87r1nyzogg.fsf@nanos.tec.linutronix.de> <20201210152618.GB23951@fuller.cnet> <87zh2lib8l.fsf@nanos.tec.linutronix.de> <20201211002703.GA47016@fuller.cnet> <87v9d8h3lx.fsf@nanos.tec.linutronix.de> <20201211141822.GA67764@fuller.cnet> <87k0togikr.fsf@nanos.tec.linutronix.de> <20201215105927.GA3321@fuller.cnet> Date: Tue, 15 Dec 2020 23:34:46 +0100 Message-ID: <877dpiu29l.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 15 2020 at 07:59, Marcelo Tosatti wrote: > On Fri, Dec 11, 2020 at 10:59:59PM +0100, Paolo Bonzini wrote: >> So it's still true that the time advances during live migration brownout; >> 0.1 seconds is just the final part of the live migration process. But for >> _live_ migration there is no need to design things according to "people are >> happy if their clock is off by 0.1 seconds only". > > Agree. What would be a good way to fix this? None of what's proposed is fixing the underlying problem of wreckaging CLOCK_REALTIME. Stop proliferating broken behaviour and please answer the questions I asked several times now: 1) Why has the TSC has to restart at the same value? 2) What is the technical argument that it is correct and acceptable to wreckage CLOCK_REALTIME by doing #1? Thanks, tglx