From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757660Ab3AYRTf (ORCPT ); Fri, 25 Jan 2013 12:19:35 -0500 Received: from mo-p00-ob.rzone.de ([81.169.146.161]:18871 "EHLO mo-p00-ob.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757645Ab3AYRTb (ORCPT ); Fri, 25 Jan 2013 12:19:31 -0500 X-RZG-AUTH: :P2EQZWCpfu+qG7CngxMFH1J+zrwiavkK6tmQaLfmztM8TOFGji0LFus= X-RZG-CLASS-ID: mo00 Date: Fri, 25 Jan 2013 18:19:23 +0100 From: Olaf Hering To: KY Srinivasan Cc: "linux-kernel@vger.kernel.org" , Greg KH , "Jan Beulich (JBeulich@suse.com)" Subject: Re: [PATCH] x86: Hyper-V: register clocksource only if its advertised Message-ID: <20130125171923.GA19306@aepfle.de> References: <1359121036-16309-1-git-send-email-olaf@aepfle.de> <761b736ff1854810bfe272961248e6d2@BLUPR03MB050.namprd03.prod.outlook.com> <20130125165443.GA15833@aepfle.de> <500ca90f5d3e4d4f80c7fb62c34d36f0@BLUPR03MB050.namprd03.prod.outlook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <500ca90f5d3e4d4f80c7fb62c34d36f0@BLUPR03MB050.namprd03.prod.outlook.com> User-Agent: Mutt/1.5.21.rev5632 (2013-01-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 25, KY Srinivasan wrote: > My fear is that there is no guarantee that Xen would not emulate this > feature in the spirit of making Hyper-V emulation "more" complete. > Since all this problem is because Xen thinks it is running a viridian > domain (when in fact it is running Linux), I felt we should explore > why the viridian tag got set for a Linux VM. If we can fix that we > would have a solution that does not depend upon assuming that Xen > would not emulate a particular Hyper-V feature. In my opinion this logic is backwards. A host provides a set of functionality/features to a given guest, no matter what runs inside the guest. And the guest can query the feature list and configure itself accordingly. In this specific case the guest finds feature A (the cpuid result) and expects that feature B (a clock source) is present as well, even if feature B has its very own availability flag. Maybe I miss your point. Olaf