From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: [PATCH] kvm_para_available() should check hypervisor bit before accessing hypervisor cpuid leaf. Date: Wed, 2 May 2012 15:09:28 +0300 Message-ID: <20120502120928.GN22191@redhat.com> References: <20120430114549.GA22191@redhat.com> <4F9FDC24.5090509@redhat.com> <20120501125546.GI22191@redhat.com> <4F9FDE35.4060100@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm@vger.kernel.org, mtosatti@redhat.com, mst@redhat.com To: Avi Kivity Return-path: Received: from mx1.redhat.com ([209.132.183.28]:35914 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753534Ab2EBMJa (ORCPT ); Wed, 2 May 2012 08:09:30 -0400 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q42C9TJI018760 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 2 May 2012 08:09:30 -0400 Content-Disposition: inline In-Reply-To: <4F9FDE35.4060100@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, May 01, 2012 at 03:59:33PM +0300, Avi Kivity wrote: > On 05/01/2012 03:55 PM, Gleb Natapov wrote: > > On Tue, May 01, 2012 at 03:50:44PM +0300, Avi Kivity wrote: > > > On 04/30/2012 02:45 PM, Gleb Natapov wrote: > > > > This couid range does not exist on real HW and Intel spec says that > > > > "Information returned for highest basic information leaf" will be > > > > returned. Not very well defined. > > > > > > > > > > Correct in principle. But IIRC some old qemus supported the kvm cpuid > > > range without setting the hypervisor bit. > > > > > How old? > > commit e19967a0e00c7af4efd2f2db12a7d5d7f0b387f7 > Author: Avi Kivity > Date: Tue Apr 22 11:44:19 2008 +0300 > > Set "hypervisor present" cpuid bit > > This tells Microsoft guests that they are running under a hypervisor. > > Signed-off-by: Avi Kivity > $ git describe --contains e19967a0e00c > kvm-80rc2~489 > Since latest Windowses will not run on such old version correctly (may use tsc for QPC) may be dropping support for Linuxes past 3.4 is a possibility too? -- Gleb.