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=-2.2 required=3.0 tests=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 A86F9C4CECF for ; Mon, 23 Sep 2019 16:48:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8357E20882 for ; Mon, 23 Sep 2019 16:48:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2437522AbfIWQsb (ORCPT ); Mon, 23 Sep 2019 12:48:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59962 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387750AbfIWQsa (ORCPT ); Mon, 23 Sep 2019 12:48:30 -0400 Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1E5C885536 for ; Mon, 23 Sep 2019 16:48:30 +0000 (UTC) Received: by mail-wm1-f71.google.com with SMTP id m16so1895756wmg.8 for ; Mon, 23 Sep 2019 09:48:30 -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:openpgp:message-id :date:user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=tZRb6baOmGI150lVZ1gc8cSyiavau4pWVjiukU4sc/o=; b=gPTgjE4t2oF0opgtVKmOvv8gCz9U8OxEyIUsp8oDPO1m2HSEzUqRk4BCsD0nmgeEo2 kUslNS31MmG/mXop9Tw4nSe1xGIM21MJc3HBgLmXiZd6t9VpDpxGmpU/cIl7EsKgsU+f fLyPWp7seC6JsHcouVzSShoKgvPErb/VBBJXUcjAjunRCdfLXB7l2fxr0HUeKqQEN2so yET4afjlWei8PYc0B8CrC0L8G2xNzKTxw/UQInCQrbNiVMLMZdjQ5kHIohXfres0Ug94 qhKQzkM++DaPHQ0sGPxIvBn3FKdMjVGjyY2+swBH6Mwnz4eHbXJe+p5pKVv1wVvq+AB9 xvmA== X-Gm-Message-State: APjAAAVuQ4WWfa6bxMnUfd0KHEO5Dn2/Y8lpTBykyQw8LP6d4jqOCwc4 BVG3Q1hBfFLHeLZPnGVAPSYnN214LJjSdnCURiB98iNL6hmgYrlskbvvEyf0qAvkSU5McZRLzgf /IYu3LNgMlPnEzj6P3oyjfr6k X-Received: by 2002:a1c:5fd6:: with SMTP id t205mr435306wmb.124.1569257308763; Mon, 23 Sep 2019 09:48:28 -0700 (PDT) X-Google-Smtp-Source: APXvYqwKleoftvyPkeoDX6aFTInlvLMkcvJSxl8ouKtBOQtpSvrSkEsMlpES5OZY/GzkKzpGkare/g== X-Received: by 2002:a1c:5fd6:: with SMTP id t205mr435269wmb.124.1569257308463; Mon, 23 Sep 2019 09:48:28 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:9520:22e6:6416:5c36? ([2001:b07:6468:f312:9520:22e6:6416:5c36]) by smtp.gmail.com with ESMTPSA id m62sm16138307wmm.35.2019.09.23.09.48.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Sep 2019 09:48:27 -0700 (PDT) Subject: Re: [PATCH 2/3] KVM: x86: hyper-v: set NoNonArchitecturalCoreSharing CPUID bit when SMT is impossible To: Peter Zijlstra , Vitaly Kuznetsov Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, x86@kernel.org, =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Sean Christopherson , Jim Mattson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Michael Kelley , Roman Kagan References: <20190916162258.6528-1-vkuznets@redhat.com> <20190916162258.6528-3-vkuznets@redhat.com> <20190923153713.GF2369@hirez.programming.kicks-ass.net> From: Paolo Bonzini Openpgp: preference=signencrypt Message-ID: <06687f31-0941-46ad-e05c-cb3cfe211051@redhat.com> Date: Mon, 23 Sep 2019 18:48:26 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190923153713.GF2369@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23/09/19 17:37, Peter Zijlstra wrote: >> This patch reports NoNonArchitecturalCoreSharing bit in to userspace in the >> first case. The second case is outside of KVM's domain of responsibility >> (as vCPU pinning is actually done by someone who manages KVM's userspace - >> e.g. libvirt pinning QEMU threads). > This is purely about guest<->guest MDS, right? Ie. not worse than actual > hardware. Even within the same guest. If vCPU 1 is on virtual core 1 and vCPU 2 is on virtual core 2, but they can share the same physical core, core scheduling in the guest can do nothing about it. Paolo