From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752220Ab3GXGzS (ORCPT ); Wed, 24 Jul 2013 02:55:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55146 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751710Ab3GXGzQ (ORCPT ); Wed, 24 Jul 2013 02:55:16 -0400 Message-ID: <51EF7A2A.6040003@redhat.com> Date: Wed, 24 Jul 2013 14:54:34 +0800 From: Jason Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130623 Thunderbird/17.0.7 MIME-Version: 1.0 To: "H. Peter Anvin" CC: KY Srinivasan , "tglx@linutronix.de" , "mingo@redhat.com" , "x86@kernel.org" , "gleb@redhat.com" , "pbonzini@redhat.com" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 4/4] x86: properly handle kvm emulation of hyperv References: <1374572465-15278-1-git-send-email-jasowang@redhat.com> <1374572465-15278-4-git-send-email-jasowang@redhat.com> <51EE97BD.4050402@zytor.com> <51EF59FB.8040207@redhat.com> <51EF5C9C.6070403@zytor.com> In-Reply-To: <51EF5C9C.6070403@zytor.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/24/2013 12:48 PM, H. Peter Anvin wrote: > On 07/23/2013 09:37 PM, Jason Wang wrote: >> On 07/23/2013 10:48 PM, H. Peter Anvin wrote: >>> On 07/23/2013 06:55 AM, KY Srinivasan wrote: >>>> This strategy of hypervisor detection based on some detection order IMHO is not >>>> a robust detection strategy. The current scheme works since the only hypervisor emulated >>>> (by other hypervisors happens to be Hyper-V). What if this were to change. >>>> >>> One strategy would be to pick the *last* one in the CPUID list, since >>> the ones before it are logically the one(s) being emulated... >>> >>> -hpa >>> >> How about simply does a reverse loop from 0x40010000 to 0x40010000? >> > Not all systems like being poked too far into hyperspace. Just remember > the last match and walk the list. > > -hpa > Ok, but it raises a question - how to know it was the 'last' match without knowing all signatures of other hyper-visor?