Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754863AbZIQGc2 (ORCPT ); Thu, 17 Sep 2009 02:32:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754169AbZIQGc1 (ORCPT ); Thu, 17 Sep 2009 02:32:27 -0400 Received: from smtp.eu.citrix.com ([62.200.22.115]:6432 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754699AbZIQGc0 (ORCPT ); Thu, 17 Sep 2009 02:32:26 -0400 X-Greylist: delayed 582 seconds by postgrey-1.27 at vger.kernel.org; Thu, 17 Sep 2009 02:32:26 EDT X-IronPort-AV: E=Sophos;i="4.44,402,1249257600"; d="scan'208";a="7119339" User-Agent: Microsoft-Entourage/12.20.0.090605 Date: Thu, 17 Sep 2009 07:22:44 +0100 Subject: Re: [Xen-devel] [RFC][PATCH 03/10] xen/hybrid: Xen Hybrid Extension initialization From: Keir Fraser To: Jeremy Fitzhardinge , Sheng Yang CC: Jeremy Fitzhardinge , xen-devel , Eddie Dong , "linux-kernel@vger.kernel.org" , Jun Nakajima Message-ID: Thread-Topic: [Xen-devel] [RFC][PATCH 03/10] xen/hybrid: Xen Hybrid Extension initialization Thread-Index: Aco3C6mnFE8s5HAkQ0WALkQ4pbhd6QAU5qZB In-Reply-To: <4AB1496B.9070705@goop.org> Mime-version: 1.0 Content-type: text/plain; charset="US-ASCII" Content-transfer-encoding: 7bit X-OriginalArrivalTime: 17 Sep 2009 06:22:47.0362 (UTC) FILETIME=[4641D220:01CA375F] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1172 Lines: 29 On 16/09/2009 21:24, "Jeremy Fitzhardinge" wrote: >> Guest would detect Hybrid capability using CPUID 0x40000002.edx, then call >> HVMOP_enable_hybrid hypercall to enable hybrid support in hypervisor. >> > > I think having an option to put PV guests into an HVM container is a > good one, but as I mentioned in the other mail, I don't think this is > the right approach. > > It would be much better to make it so that an unmodified guest works in > such a mode; even with no specific optimisations the guest would get > benefit from faster kernel<->usermode switches. By unmodified you mean ordinary PV guest? It's an interesting comparison -- PVing an HVM guest, versus HVMing (to some extent) a PV guest. -- Keir > Then we can add specific optimisations to take advantage of, say, > running in ring 0 (=fast syscalls) and having access to HAP hardware > (=direct pagetable updates, no pinning). -- 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/