Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753991AbdIDTcn convert rfc822-to-8bit (ORCPT ); Mon, 4 Sep 2017 15:32:43 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51282 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753953AbdIDTcl (ORCPT ); Mon, 4 Sep 2017 15:32:41 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com F18FD15E918 Authentication-Results: ext-mx04.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx04.extmail.prod.ext.phx2.redhat.com; spf=fail smtp.mailfrom=longman@redhat.com Subject: Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV spinlock To: Peter Zijlstra , Oscar Salvador Cc: Ingo Molnar , Paolo Bonzini , "H . Peter Anvin" , Thomas Gleixner , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org References: <20170904142836.15446-1-osalvador@suse.de> <20170904144011.gp7hpis6usjehbuf@hirez.programming.kicks-ass.net> From: Waiman Long Organization: Red Hat Message-ID: Date: Mon, 4 Sep 2017 15:32:39 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20170904144011.gp7hpis6usjehbuf@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Content-Language: en-US X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Mon, 04 Sep 2017 19:32:41 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1003 Lines: 23 On 09/04/2017 10:40 AM, Peter Zijlstra wrote: > On Mon, Sep 04, 2017 at 04:28:36PM +0200, Oscar Salvador wrote: >> This is just a resend of Waiman Long's patch. >> I could not find why it was not merged to upstream, so I thought >> to give it another chance. >> What follows is what Waiman Long wrote. >> >> Xen has an kernel command line argument "xen_nopvspin" to disable >> paravirtual spinlocks. This patch adds a similar "kvm_nopvspin" >> argument to disable paravirtual spinlocks for KVM. This can be useful >> for testing as well as allowing administrators to choose unfair lock >> for their KVM guests if they want to. > For testing its trivial to hack your kernel and I don't feel this is > something an Admin can make reasonable decisions about. I almost forgot about this patch that I sent quite a while ago. I was sending this patch out mainly to maintain consistency between KVM and Xen. This patch is not that important to me, and that is why I didn't push it further. Cheers, Longman