From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 26/26] KVM: PPC: Add Documentation about PV interface Date: Sun, 27 Jun 2010 11:34:06 +0300 Message-ID: <4C270CFE.2040600@redhat.com> References: <1277508314-915-1-git-send-email-agraf@suse.de> <1277508314-915-27-git-send-email-agraf@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm-ppc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, KVM list , linuxppc-dev To: Alexander Graf Return-path: In-Reply-To: <1277508314-915-27-git-send-email-agraf-l3A5Bk7waGM@public.gmane.org> Sender: kvm-ppc-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: kvm.vger.kernel.org On 06/26/2010 02:25 AM, Alexander Graf wrote: > We just introduced a new PV interface that screams for documentation. So here > it is - a shiny new and awesome text file describing the internal works of > the PPC KVM paravirtual interface. > > > +Querying for existence > +====================== > + > +To find out if we're running on KVM or not, we overlay the PVR register. Usually > +the PVR register contains an id that identifies your CPU type. If, however, you > +pass KVM_PVR_PARA in the register that you want the PVR result in, the register > +still contains KVM_PVR_PARA after the mfpvr call. > + > + LOAD_REG_IMM(r5, KVM_PVR_PARA) > + mfpvr r5 > + [r5 still contains KVM_PVR_PARA] > + > +Once determined to run under a PV capable KVM, you can now use hypercalls as > +described below. > On x86 we allow host userspace to determine whether the guest sees the paravirt interface (and what features are exposed). This allows you to live migrate from a newer host to an older host, by not exposing the newer features. -- error compiling committee.c: too many arguments to function