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,NICE_REPLY_A,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 83CD5C4332D for ; Mon, 15 Mar 2021 16:24:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 66BBE64F35 for ; Mon, 15 Mar 2021 16:24:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232465AbhCOQYD (ORCPT ); Mon, 15 Mar 2021 12:24:03 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:53544 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232445AbhCOQXo (ORCPT ); Mon, 15 Mar 2021 12:23:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615825424; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=3wdZ2o2UMvoAMlrjWoFf17ZzvfbNLm3Hw3Ulncm86lM=; b=heE/TPvyDvuRjmUu1q8P5l2hLARjFkXSMtq5VzX+fmOnXStXygb8PnsbwP1Hg7bgNXsLw5 a4BP8coNQrd71GTHY9kCJAye3Lze1GgMky3FJKQAD99S1v6ZHbE5CBHkKLswfr5wbfwmCo x1jyM8C/9NJ9YCcZxI8D3uRARb15OBc= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-273-BPA3bdVYNFOvdqzVgFWEKg-1; Mon, 15 Mar 2021 12:23:42 -0400 X-MC-Unique: BPA3bdVYNFOvdqzVgFWEKg-1 Received: by mail-wm1-f70.google.com with SMTP id y9so3013305wma.4 for ; Mon, 15 Mar 2021 09:23:42 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=3wdZ2o2UMvoAMlrjWoFf17ZzvfbNLm3Hw3Ulncm86lM=; b=dXQcQJkpv9E//ZQ+2jftY+tE9CungrCqyWQ2h3KwbbenejnMwT/diyNcFf29Y1bITH m8TAgyTgPeiC5v4XqriMoQStSKsxuk0eew1Ql0dwXEUT8Op88CPk8OkCE3Wy2cDjh1eq LQ9yNsf7XwS525zGYojCT/YHJRPeTdSo2ioGhl8T4Pa29IVHvAABgBY2FPhEXWeHEo1G Q89tJmrHfp1IjlAsr48pKBsLygZ9EPianxu9hCHhLNYcSByGo/WrMJanJGGu77BsTcmV pfoaYvyZcg0ZrO2o0EmaR2gDQEH/df3Yw2FpS4pZuCeiw7F/v+d3Cq3dNn6yzWo4bsEi LvaQ== X-Gm-Message-State: AOAM532G0B9iypoMZlMh9oouIXiVrGVPpUj+gH/tjt0vlEDmQHQfdo6g BF0aHFCftDvFt3CVy4RLL2CcHZsTYcjCS67DooiZoFr08tTPY89sSd6KR6LdsY2PJ1xyj46mAK1 duEAjGVHx28gy X-Received: by 2002:a7b:c38d:: with SMTP id s13mr499085wmj.44.1615825420886; Mon, 15 Mar 2021 09:23:40 -0700 (PDT) X-Google-Smtp-Source: ABdhPJx48wpeFGkULhUPziop+7I6XIylLHEf7uh9fFC7HbtW8j8rz7mfnHbK8sHo+NqkbmpdQHaE9Q== X-Received: by 2002:a7b:c38d:: with SMTP id s13mr499067wmj.44.1615825420735; Mon, 15 Mar 2021 09:23:40 -0700 (PDT) Received: from ?IPv6:2001:b07:add:ec09:c399:bc87:7b6c:fb2a? ([2001:b07:add:ec09:c399:bc87:7b6c:fb2a]) by smtp.gmail.com with ESMTPSA id v13sm22098238wrt.45.2021.03.15.09.23.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 15 Mar 2021 09:23:40 -0700 (PDT) Subject: Re: [PATCH 2/4] KVM: x86: hyper-v: Prevent using not-yet-updated TSC page by secondary CPUs To: Vitaly Kuznetsov , kvm@vger.kernel.org Cc: Sean Christopherson , Wanpeng Li , Jim Mattson , Marcelo Tosatti References: <20210315143706.859293-1-vkuznets@redhat.com> <20210315143706.859293-3-vkuznets@redhat.com> <6b392d7e-8135-53a9-9040-f6f5e316c6cb@redhat.com> <87im5s8l9g.fsf@vitty.brq.redhat.com> From: Paolo Bonzini Message-ID: <92bccdca-b6bb-5c09-c5a1-5c75e5a3887d@redhat.com> Date: Mon, 15 Mar 2021 17:23:39 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <87im5s8l9g.fsf@vitty.brq.redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 15/03/21 16:55, Vitaly Kuznetsov wrote: >> I think we should instead write 0 to the page in kvm_gen_update_masterclock. > > We can do that but we will also need to invalidate > hv->tsc_ref.tsc_sequence to prevent MSR based clocksource > (HV_X64_MSR_TIME_REF_COUNT -> get_time_ref_counter()) from using stale > hv->tsc_ref.tsc_scale/tsc_offset values (in case we had them > calculated). Yes, we're talking about the same thing (invalidating tsc_sequence is done by writing 0 to it). Paolo > Also, we can't really disable TSC page for nested scenario when guest > opted for reenlightenment (PATCH4) but we're not going to update the > page anyway so there's not much different. >