From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: drop -enable-nesting Date: Mon, 30 May 2011 17:59:23 +0200 Message-ID: <4DE3BEDB.3030108@siemens.com> References: <4DDAD5CF.5050805@redhat.com> <4DE0B4B1.1000407@web.de> <20110530081847.GC27062@amd.com> <4DE3A3EC.80201@siemens.com> <20110530143846.GA2957@fermat.math.technion.ac.il> <4DE3B1E2.7020006@siemens.com> <20110530151623.GA3630@fermat.math.technion.ac.il> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: john cooper , "Roedel, Joerg" , Anthony Liguori , "qemu-devel@nongnu.org" , kvm To: "Nadav Har'El" Return-path: In-Reply-To: <20110530151623.GA3630@fermat.math.technion.ac.il> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org Sender: qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org List-Id: kvm.vger.kernel.org On 2011-05-30 17:16, Nadav Har'El wrote: > On Mon, May 30, 2011, Jan Kiszka wrote about "Re: drop -enable-nesting": >>> "-enable-nesting" could remain as a synonym for enabling either VMX or SVM >>> in the guest, depending on what was available in the host (because KVM now >>> supports both nested SVM and nested VMX, but not SVM-on-VMX or vice versa). >> >> Why? Once nesting is stable (I think SVM already is), there is no reason >> for an explicit enable. And you can always mask it out via -cpu. > > As far as I understand (and this was previously discussed on the QEMU mailing > list), the default emulated CPU does not include the "vmx" capability, and you > need to enable it with something like "-cpu qemu64,+vmx" (or "-cpu host"). qemu64 is an artificial AMD model. Adding VMX to it may have interesting effects on the guests. Better use host or a recent Intel model. > > I am not sure if it does enable the "svm" capability. If it does, it isn't > useful when KVM is enabled and the underlying host has VMX, not SVM. That's what KVM is supposed to filter based on the host's capabilities. I bet it does already. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:49227) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QR4sQ-0007oN-5F for qemu-devel@nongnu.org; Mon, 30 May 2011 11:59:35 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QR4sP-00086v-6u for qemu-devel@nongnu.org; Mon, 30 May 2011 11:59:34 -0400 Received: from thoth.sbs.de ([192.35.17.2]:27628) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QR4sO-00086T-UM for qemu-devel@nongnu.org; Mon, 30 May 2011 11:59:33 -0400 Message-ID: <4DE3BEDB.3030108@siemens.com> Date: Mon, 30 May 2011 17:59:23 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <4DDAD5CF.5050805@redhat.com> <4DE0B4B1.1000407@web.de> <20110530081847.GC27062@amd.com> <4DE3A3EC.80201@siemens.com> <20110530143846.GA2957@fermat.math.technion.ac.il> <4DE3B1E2.7020006@siemens.com> <20110530151623.GA3630@fermat.math.technion.ac.il> In-Reply-To: <20110530151623.GA3630@fermat.math.technion.ac.il> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] drop -enable-nesting List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Nadav Har'El Cc: john cooper , "Roedel, Joerg" , Anthony Liguori , "qemu-devel@nongnu.org" , kvm On 2011-05-30 17:16, Nadav Har'El wrote: > On Mon, May 30, 2011, Jan Kiszka wrote about "Re: drop -enable-nesting": >>> "-enable-nesting" could remain as a synonym for enabling either VMX or SVM >>> in the guest, depending on what was available in the host (because KVM now >>> supports both nested SVM and nested VMX, but not SVM-on-VMX or vice versa). >> >> Why? Once nesting is stable (I think SVM already is), there is no reason >> for an explicit enable. And you can always mask it out via -cpu. > > As far as I understand (and this was previously discussed on the QEMU mailing > list), the default emulated CPU does not include the "vmx" capability, and you > need to enable it with something like "-cpu qemu64,+vmx" (or "-cpu host"). qemu64 is an artificial AMD model. Adding VMX to it may have interesting effects on the guests. Better use host or a recent Intel model. > > I am not sure if it does enable the "svm" capability. If it does, it isn't > useful when KVM is enabled and the underlying host has VMX, not SVM. That's what KVM is supposed to filter based on the host's capabilities. I bet it does already. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux