From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: drop -enable-nesting Date: Mon, 30 May 2011 17:15:49 +0200 Message-ID: <4DE3B4A5.6050509@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> <20110530151020.GB7855@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Cc: john cooper , Anthony Liguori , Nadav Har'El , kvm , "qemu-devel@nongnu.org" To: "Roedel, Joerg" Return-path: In-Reply-To: <20110530151020.GB7855@amd.com> 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 17:10, Roedel, Joerg wrote: > On Mon, May 30, 2011 at 11:04:02AM -0400, Jan Kiszka wrote: >> On 2011-05-30 16:38, Nadav Har'El wrote: >>> On Mon, May 30, 2011, Jan Kiszka wrote about "drop -enable-nesting (w= as: [PATCH 3/7] cpu model bug fixes and definition corrections...)": >>>> On 2011-05-30 10:18, Roedel, Joerg wrote: >>>>> On Sat, May 28, 2011 at 04:39:13AM -0400, Jan Kiszka wrote: >>>>> >>>>>> J=EF=BF=BDrg, how to deal with -enable-nesting in qemu-kvm to alig= n behavior >>>>>> with upstream? >>>>> >>>>> My personal preference is to just remove it. In upstream-qemu it is >>>>> enabled/disabled by +/-svm. -enable-nesting is just a historic thin= g >>>>> which can be wiped out. >>> >>> "-enable-nesting" could remain as a synonym for enabling either VMX o= r SVM >>> in the guest, depending on what was available in the host (because KV= M now >>> supports both nested SVM and nested VMX, but not SVM-on-VMX or vice v= ersa). >> >> Why? Once nesting is stable (I think SVM already is), there is no reas= on >> for an explicit enable. And you can always mask it out via -cpu. >> >> BTW, what are the defaults for SVM right now in qemu-kvm and upstream? >> Enable if the modeled CPU supports it? >=20 > qemu-kvm still needs -enable-nesting, otherwise it is disabled. Upstrea= m > qemu should enable it unconditionally (can be disabled with -cpu ,-svm). Then let's start with aligning qemu-kvm defaults to upstream? I guess that's what the diff I was citing yesterday is responsible for. In the same run, -enable-nesting could dump a warning on the console that this switch is obsolete and will be removed from future versions. For VMX, I would suggest to keep it off by default until it matured, asking the user to issue -cpu ...,+vmx. Jan --=20 Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux