From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753870AbdIDOkS (ORCPT ); Mon, 4 Sep 2017 10:40:18 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:59036 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753736AbdIDOkQ (ORCPT ); Mon, 4 Sep 2017 10:40:16 -0400 Date: Mon, 4 Sep 2017 16:40:12 +0200 From: Peter Zijlstra To: 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, Waiman Long Subject: Re: [PATCH resend] x86,kvm: Add a kernel parameter to disable PV spinlock Message-ID: <20170904144011.gp7hpis6usjehbuf@hirez.programming.kicks-ass.net> References: <20170904142836.15446-1-osalvador@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170904142836.15446-1-osalvador@suse.de> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. So why? In general less knobs is better.