From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:45682) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1StJeV-0002Ei-54 for qemu-devel@nongnu.org; Mon, 23 Jul 2012 10:30:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1StJeP-0007y6-CI for qemu-devel@nongnu.org; Mon, 23 Jul 2012 10:30:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48714) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1StJeP-0007xw-2g for qemu-devel@nongnu.org; Mon, 23 Jul 2012 10:30:21 -0400 Message-ID: <500D5FEE.1010006@redhat.com> Date: Mon, 23 Jul 2012 17:30:06 +0300 From: Avi Kivity MIME-Version: 1.0 References: <1342811652-16931-1-git-send-email-peter.maydell@linaro.org> <500A52BF.9080207@web.de> <500D42E2.4000009@redhat.com> <500D4D12.1060603@redhat.com> <500D53DB.5080005@redhat.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] kvm: Move kvm_allows_irq0_override() to target-i386 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: kvm , patches@linaro.org, Marcelo Tosatti , Alexander Graf , qemu-devel@nongnu.org, Jan Kiszka On 07/23/2012 04:50 PM, Peter Maydell wrote: >> >> Yet. > > There is no mechanism in the virtualization extensions to either > trap on or present a false value for guest accesses to the CPSR > mode bits. So you can't make the guest OS think it is in Hypervisor > mode. Therefore you can't provide the guest with the virtualization > extensions. (The same argument applies for Monitor mode and means > you can't provide the Security extensions (TrustZone) to the guest > either.) I guess you could handle all code in the guest hypervisor > under TCG but implementing a hybrid TCG+KVM mode would be a lot > of effort and probably not really perform very well anyway... Gaah, people add virtualization extensions to fix an ISA's non-virtualizability, then do the same mistake again. But I was only joking. Nested virtualization is interesting technically but so far I haven't seen any huge or even small uptake. -- error compiling committee.c: too many arguments to function