Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934272AbdIYIgI (ORCPT ); Mon, 25 Sep 2017 04:36:08 -0400 Received: from merlin.infradead.org ([205.233.59.134]:39632 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932364AbdIYIgG (ORCPT ); Mon, 25 Sep 2017 04:36:06 -0400 Date: Mon, 25 Sep 2017 10:35:57 +0200 From: Peter Zijlstra To: Marcelo Tosatti Cc: Konrad Rzeszutek Wilk , mingo@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: [patch 3/3] x86: kvm guest side support for KVM_HC_RT_PRIO hypercall Message-ID: <20170925083557.e6zwudms2pyxnhju@hirez.programming.kicks-ass.net> References: <20170921114039.466130276@redhat.com> <20170921133653.GO26248@char.us.oracle.com> <20170921140628.zliqlz7mrlqs5pzz@hirez.programming.kicks-ass.net> <20170922011039.GB20133@amt.cnet> <20170922100004.ydmaxvgpc2zx7j25@hirez.programming.kicks-ass.net> <20170922121640.GA29589@amt.cnet> <20170922123107.fjh2yfwnej73trim@hirez.programming.kicks-ass.net> <20170922123639.GB29589@amt.cnet> <20170922125951.siaci6yp3vec4i3i@hirez.programming.kicks-ass.net> <20170925015256.GA5140@amt.cnet> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170925015256.GA5140@amt.cnet> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 599 Lines: 14 On Sun, Sep 24, 2017 at 10:52:58PM -0300, Marcelo Tosatti wrote: > On Fri, Sep 22, 2017 at 02:59:51PM +0200, Peter Zijlstra wrote: > > Your patch is voodoo programming. You don't solve the actual problem, > > you try and paper over it. > > Priority boosting on a particular section of code is voodoo programming? Yes, because there's nothing that prevents said section of code from triggering the exact problem you're trying to avoid. The real fix is making sure the problem cannot happen to begin with, which is done by fixing the interaction between the VCPU and that emulation thread thing.