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=-2.4 required=3.0 tests=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 6DE9FC55181 for ; Mon, 20 Apr 2020 21:10:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4619B2078C for ; Mon, 20 Apr 2020 21:10:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="IaLKHa1P" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726859AbgDTVKH (ORCPT ); Mon, 20 Apr 2020 17:10:07 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:27830 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725774AbgDTVKG (ORCPT ); Mon, 20 Apr 2020 17:10:06 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587417005; 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=7lDCFaFUw4R9AWRYUPjaGqLtTptNqr4/gsP5Cs91YoI=; b=IaLKHa1PFuA/zjjdIBFLmKdRMKCVJ9lh0yPCN6+ZetUHxOnTosHhGYu4brxt1WnXm/oo7y FRclpDVS+1/h6W22/9AgfqGkd+8lazk1c9VuZ8ORrEZXgD+Mt8C0bvqoiTbf4AJ7dPd554 9YU52jBnpEuTHckXhMP/vbSxbQCDe4M= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-163-SGX-p1vmMweJlmMJgTzKJA-1; Mon, 20 Apr 2020 17:09:57 -0400 X-MC-Unique: SGX-p1vmMweJlmMJgTzKJA-1 Received: by mail-wr1-f72.google.com with SMTP id i10so6373886wrq.8 for ; Mon, 20 Apr 2020 14:09:56 -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=7lDCFaFUw4R9AWRYUPjaGqLtTptNqr4/gsP5Cs91YoI=; b=b4WX2Mk+mEnH1LV3llhLOxyVQVqRSyTSto3S7y+NEZ7QEDIGaFSVStSuSKGAboKd8d MBvqMBMvdoq/aWI476FUxEpYunls/QUFP/3ohbd/lMum9ee1HvWyHkaHxjxrFnM+ylVS 0QQ7hagKLr0ywXd5Zksb+OLT4tFFPNQnV0VUGIw3BbaptYjjnryfYvYa0/gklrX4tpqU QKJbbGzzrK889NZsl+yr2kN36fBHV6lx02PWgN7sDmSxnOYAgmPtGXDtea/pNA2KGNS4 OsRR8uS3xtr9jNZT1afwq4h5G0LZkHhgyuMlS0sSThb7A+7QlTb0uV6H2uXz5x5cIc0w 5OiA== X-Gm-Message-State: AGi0PuYvCdSj6lBFYBIz9DsHSKvHC/d8PdObRIzefLU9zPx+zVMicfLq O8rJdHJ38H3ulzn267OhGSty4Ps174z4z2gzn0ccCs5ddnTzLqTo7PBu+RFFW5nvfY/Ot2YUk1G Gd+FwUlaJ7X292zEIgEZ8CvHV X-Received: by 2002:a1c:2e0a:: with SMTP id u10mr1274789wmu.119.1587416995501; Mon, 20 Apr 2020 14:09:55 -0700 (PDT) X-Google-Smtp-Source: APiQypK6od6W0dj1gZbWeyxDBs/v6PJZ1fc/3Z8V3Hi0ONmnXmb1L3h9dzlN2r24n5ADl1uYH1Bh5A== X-Received: by 2002:a1c:2e0a:: with SMTP id u10mr1274770wmu.119.1587416995274; Mon, 20 Apr 2020 14:09:55 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:5c18:5523:c13e:fa9f? ([2001:b07:6468:f312:5c18:5523:c13e:fa9f]) by smtp.gmail.com with ESMTPSA id j13sm901220wro.51.2020.04.20.14.09.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 20 Apr 2020 14:09:54 -0700 (PDT) Subject: Re: [PATCH] kvm: add capability for halt polling To: Jon Cargille , Vitaly Kuznetsov Cc: David Matlack , Sean Christopherson , Wanpeng Li , Jim Mattson , Joerg Roedel , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200417221446.108733-1-jcargill@google.com> <87d083td9f.fsf@vitty.brq.redhat.com> From: Paolo Bonzini Message-ID: <02039a7b-01b4-ea5c-bd73-100ea753bf5e@redhat.com> Date: Mon, 20 Apr 2020 23:09:47 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: 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 20/04/20 20:47, Jon Cargille wrote: >> Is it safe to allow any value from userspace here or would it maybe make >> sense to only allow [0, global halt_poll_ns]? > I believe that any value is safe; a very large value effectively disables > halt-polling, which is equivalent to setting a value of zero to explicitly > disable it, which is legal. Doesn't a large value make KVM poll all the time? But you could do that just by running "for (;;)" so there's no reason to limit the parameter. Paolo