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=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 4B87DC433E6 for ; Thu, 18 Mar 2021 18:31:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0572C64F38 for ; Thu, 18 Mar 2021 18:31:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230164AbhCRSbZ (ORCPT ); Thu, 18 Mar 2021 14:31:25 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:27146 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231590AbhCRSbR (ORCPT ); Thu, 18 Mar 2021 14:31:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616092276; 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=0mw/nf+8C6A4qj8FRDm7YP6EnE67XsUZD9T0VjBOeds=; b=Ugud/K9WhLbutfzY03Sj6dbcYqtt0kFeE9Ln12dPMR0fybL0i9Go+Sxlvlx1UTabZE/fD5 3pVizKHMjmFzt1/YOCO3QVhHEfC+wJp0fWNpPIMjZXPh/Kvj4SfZS6Wra/kGH+gmEdqF43 BIkYtGu+hGd1kbNk/o9i6OzN/TFiIrY= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-330-_3Zb7MdKMvmHMTN_EGnyFw-1; Thu, 18 Mar 2021 14:31:14 -0400 X-MC-Unique: _3Zb7MdKMvmHMTN_EGnyFw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 6D3C91034B34; Thu, 18 Mar 2021 18:31:13 +0000 (UTC) Received: from fuller.cnet (ovpn-112-2.gru2.redhat.com [10.97.112.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 055A860CD7; Thu, 18 Mar 2021 18:31:13 +0000 (UTC) Received: by fuller.cnet (Postfix, from userid 1000) id 75D704188684; Thu, 18 Mar 2021 15:30:42 -0300 (-03) Date: Thu, 18 Mar 2021 15:30:42 -0300 From: Marcelo Tosatti To: Paolo Bonzini Cc: Vitaly Kuznetsov , kvm@vger.kernel.org, Sean Christopherson , Wanpeng Li , Jim Mattson Subject: Re: [PATCH v2 2/4] KVM: x86: hyper-v: Prevent using not-yet-updated TSC page by secondary CPUs Message-ID: <20210318183042.GA42884@fuller.cnet> References: <20210316143736.964151-1-vkuznets@redhat.com> <20210316143736.964151-3-vkuznets@redhat.com> <20210318170208.GB36190@fuller.cnet> <20210318180446.GA41953@fuller.cnet> <5634f6c9-bee9-ae07-c8ce-8e79bd2bd1a7@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5634f6c9-bee9-ae07-c8ce-8e79bd2bd1a7@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Mar 18, 2021 at 07:05:49PM +0100, Paolo Bonzini wrote: > On 18/03/21 19:04, Marcelo Tosatti wrote: > > > > > > Not clear why this is necessary, if the choice was to not touch TSC page > > > at all, when invariant TSC is supported on the host... > > > > s/invariant TSC/TSC scaling/ > > > > > Ah, OK, this is not for the migration with iTSC on destination case, > > > but any call to kvm_gen_update_masterclock, correct? > > Yes, any update can be racy. > > Paolo Which makes an unrelated KVM_REQ_MASTERCLOCK_UPDATE -> kvm_gen_update_masterclock sequence to inadvertedly reduce performance a possibility, unless i am missing something. Ah, OK, it should be enabled again at KVM_REQ_CLOCK_UPDATE. Nevermind, then.