From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: libvirt and nestedhvm. Date: Fri, 6 Jun 2014 14:33:54 +0100 Message-ID: <5391C342.3090800@citrix.com> References: <5391C1F3.9040603@netvel.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5391C1F3.9040603@netvel.net> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Alvin Starr Cc: xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 06/06/14 14:28, Alvin Starr wrote: > I am trying to shoehorn the ability to start a nested HVM into libvirt > through the libxl interface. > > Setting the nestedhvm flag is easy enough but I also need to mask the > svm_npt cpuid flags. This presumably comes from a KVM centric view where the environment running libvirtd is the host environment? > > This is where life gets interesting. > > LIbvirt seems to probe the CPUID registers to determine what flags are > available. > Libvirt then stops me from trying to mask the svm or npt flags since > they are not visible in dom0. > > So my question is. > Can I enable the svm,npt flags in dom0? Technically it is possible to make these flags appear... > Is there anything equivalent to nestedhvm for dom0? ... but being features that PV guests cannot possibly use, advertising them is a bad idea. > > or is there a way to read the raw CPU flags? > Not really. It is one of the many things on my bucketlist of basic things which need fixing with all the other Xen/libxc/toolstack cpuid work. ~Andrew