From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jan Kiszka <jan.kiszka@siemens.com>
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 <john.cooper@redhat.com>, "Roedel,
	Joerg" <Joerg.Roedel@amd.com>, Anthony Liguori <aliguori@us.ibm.com>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, kvm <kvm@vger.kernel.org>
To: "Nadav Har'El" <nyh@math.technion.ac.il>
Return-path: <qemu-devel-bounces+gceq-qemu-devel=gmane.org@nongnu.org>
In-Reply-To: <20110530151623.GA3630@fermat.math.technion.ac.il>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: </archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=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