From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751921AbbIQMdQ (ORCPT ); Thu, 17 Sep 2015 08:33:16 -0400 Received: from casper.infradead.org ([85.118.1.10]:32884 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751527AbbIQMdP (ORCPT ); Thu, 17 Sep 2015 08:33:15 -0400 Date: Thu, 17 Sep 2015 14:27:50 +0200 From: Peter Zijlstra To: Paolo Bonzini Cc: Andy Lutomirski , x86@kernel.org, KVM list , Arjan van de Ven , xen-devel , linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/3] x86/paravirt: Fix baremetal paravirt MSR ops Message-ID: <20150917122750.GH3604@twins.programming.kicks-ass.net> References: <20150917085807.GH3816@twins.programming.kicks-ass.net> <55FAA6AE.9050503@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55FAA6AE.9050503@redhat.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 17, 2015 at 01:40:30PM +0200, Paolo Bonzini wrote: > > > On 17/09/2015 10:58, Peter Zijlstra wrote: > > But the far greater problem I have with the whole virt thing is that > > you cannot use rdmsr_safe() to probe if an MSR exists at all because, as > > you told me, these virt thingies return 0 for all 'unknown' MSRs instead > > of faulting. > > At least for KVM, that behavior is opt-in (the ignore_msrs parameter) > and no distro that I know enables it by default. Ah, that would be good news. Andy earlier argued I could not rely on rdmsr_safe() faulting on unknown MSRs. If practically we can there's some code I can simplify :-)