Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754082AbYJAVf3 (ORCPT ); Wed, 1 Oct 2008 17:35:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753504AbYJAVfS (ORCPT ); Wed, 1 Oct 2008 17:35:18 -0400 Received: from mail-gx0-f16.google.com ([209.85.217.16]:41478 "EHLO mail-gx0-f16.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753346AbYJAVfQ (ORCPT ); Wed, 1 Oct 2008 17:35:16 -0400 Message-ID: <48E3ECD1.30809@codemonkey.ws> Date: Wed, 01 Oct 2008 16:34:09 -0500 From: Anthony Liguori User-Agent: Thunderbird 2.0.0.16 (X11/20080723) MIME-Version: 1.0 To: Jeremy Fitzhardinge CC: akataria@vmware.com, "avi@redhat.com" , Rusty Russell , Gerd Hoffmann , "H. Peter Anvin" , Ingo Molnar , the arch/x86 maintainers , LKML , "Nakajima, Jun" , Daniel Hecht , Zach Amsden , "virtualization@lists.linux-foundation.org" , "kvm@vger.kernel.org" Subject: Re: [RFC] CPUID usage for interaction between Hypervisors and Linux. References: <1222881242.9381.17.camel@alok-dev1> <48E3BBC1.2050607@goop.org> <1222894878.9381.63.camel@alok-dev1> <48E3E8DE.1080602@goop.org> In-Reply-To: <48E3E8DE.1080602@goop.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1065 Lines: 27 Jeremy Fitzhardinge wrote: > Alok Kataria wrote: > > I guess, but the bulk of the uses of this stuff are going to be > hypervisor-specific. You're hard-pressed to come up with any other > generic uses beyond tsc. And arguably, storing TSC frequency in CPUID is a terrible interface because the TSC frequency can change any time a guest is entered. It really should be a shared memory area so that a guest doesn't have to vmexit to read it (like it is with the Xen/KVM paravirt clock). Regards, Anthony Liguori > In general, if a hypervisor is going to put something in a special > cpuid leaf, its because there's no other good way to represent it. > Generic things are generally going to appear as an emulated piece of > the virtualized platform, in ACPI, DMI, a hardware-defined cpuid leaf, > etc... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/