From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [patch] VMX Unrestricted mode support Date: Sun, 31 May 2009 19:01:03 +0300 Message-ID: <4A22A9BF.7010302@redhat.com> References: <1243552292.25456.23.camel@mukti.sc.intel.com> <4A22A0DB.8050906@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Nitin A Kamble , kvm@vger.kernel.org To: Anthony Liguori Return-path: Received: from mx2.redhat.com ([66.187.237.31]:57633 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755142AbZEaQBG (ORCPT ); Sun, 31 May 2009 12:01:06 -0400 In-Reply-To: <4A22A0DB.8050906@codemonkey.ws> Sender: kvm-owner@vger.kernel.org List-ID: Anthony Liguori wrote: > Nitin A Kamble wrote: > >> Avi, >> >> A new VMX feature "Unrestricted Guest" feature is added in the VMX >> specification. You can look at the latest Intel processor manual for >> details of the feature here: >> >> http://www.intel.com/products/processor/manuals >> >> It allows kvm guests to run real mode and unpaged mode >> code natively in the VMX mode when EPT is turned on. With the >> unrestricted guest there is no need to emulate the guest real mode code >> in the vm86 container or in the emulator. Also the guest big real mode >> code works like native. >> >> The attached patch enhances KVM to use the unrestricted guest feature >> if available on the processor. It also adds a new kernel/module >> parameter to disable the unrestricted guest feature at the boot time. >> >> Signed-Off-By: Nitin A Kamble >> >> Thanks & Regards, >> Nitin >> >> > > It may make sense to expose this as a CAP down to userspace. > > We could possibly make better error messages in userspace when we get an > unknown vmexit failure on pre-wsm hardware. > If we see the dreaded 0x80000021 and CR0.PE=0, then we're likely seeing a real mode emulation problem. -- error compiling committee.c: too many arguments to function