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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 64161C04AB6 for ; Wed, 29 May 2019 01:25:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 378D621734 for ; Wed, 29 May 2019 01:25:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726256AbfE2BZn (ORCPT ); Tue, 28 May 2019 21:25:43 -0400 Received: from mail-wr1-f67.google.com ([209.85.221.67]:36163 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725832AbfE2BZm (ORCPT ); Tue, 28 May 2019 21:25:42 -0400 Received: by mail-wr1-f67.google.com with SMTP id s17so464724wru.3 for ; Tue, 28 May 2019 18:25:41 -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=rqj4DN+mKFOFN2ElIEBtWrUBDtgBpL5CxV4R4XTM10o=; b=RVx8hscCWqB6dFtYupixvrhbnbdxExxVQKAjrRfZQAw1TdPI7q/PkhLp0wd1ygxCot o/x4xNuwm1O8gx18DNvjxn9ZUDJ0Xk8sHtkRd1UPGSS4Z+ai7wR/gBHhpYArLC82Q96X XFgb4/iDoMiQXAQ9f9rbNmWYKcivHRwxJlWxjM/VI8YkeZMnP3irLJTI78RVDTDvy7lj xPITznJEYclHXsfmrzu8ppSs+VCbKeXKAiANbzIivdyHBrEe5myE4iEIe9mOSJNDPPtn EC19hL84R2w7UlqaQ9XyuYyh4NHSMqEJy87aE/hQCoTgkRWC2GfBJ9F0iU5UibI3m3pk Cftg== X-Gm-Message-State: APjAAAWSpxcT5qMCRBa9LBRW5jc070oJeGT5MNukUOl4LAOPII2jwMuw 2PjBnp9sjh4dl4CXRYF7R2MdAA== X-Google-Smtp-Source: APXvYqwtWVxxE2Y3KBugsv4RW0JNUGuXKYKlfAWL8wp283sVlUi5mkh0LOf0h0ykT1V8TpWOn1NBog== X-Received: by 2002:a5d:5189:: with SMTP id k9mr14487648wrv.329.1559093141154; Tue, 28 May 2019 18:25:41 -0700 (PDT) Received: from [192.168.10.150] ([93.56.166.5]) by smtp.gmail.com with ESMTPSA id s15sm10845265wrn.68.2019.05.28.18.25.39 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 28 May 2019 18:25:40 -0700 (PDT) Subject: Re: [PATCH v2 1/3] KVM: x86: add support for user wait instructions To: Peter Zijlstra , Tao Xu Cc: rkrcmar@redhat.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, sean.j.christopherson@intel.com, x86@kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, jingqi.liu@intel.com References: <20190524075637.29496-1-tao3.xu@intel.com> <20190524075637.29496-2-tao3.xu@intel.com> <20190527103003.GX2623@hirez.programming.kicks-ass.net> From: Paolo Bonzini Message-ID: Date: Wed, 29 May 2019 03:25:39 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190527103003.GX2623@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 27/05/19 12:30, Peter Zijlstra wrote: >> This patch adds support for UMONITOR, UMWAIT and TPAUSE instructions >> in kvm, and by default dont't expose it to kvm and provide a capability >> to enable it. > > I'm thinking this should be conditional on the guest being a 1:1 guest, > and I also seem to remember we have bits for that already -- they were > used to disable paravirt spinlocks for example. This should be userspace's choice. It would indeed be silly to enable this while overcommitted, but KVM doesn't really care. Paolo