On Thu, Jan 24, 2013 at 8:08 PM, Alexander Graf <ag...@suse.de> wrote:
> > On 24.01.2013, at 10:25, Stefan Hajnoczi wrote: > > > On Thu, Jan 24, 2013 at 11:40:24AM +0530, Anup Patel wrote: > >> IMHO, If we have something like Virtio-desktop specification then all > >> possible guest OSes can have support for it and different hypervisor can > >> emulate it without worrying about guest support. > > > > At this point x86 virtualization is mature and working with a mix of > > emulated x86 architecture pieces and virtio devices for > > performance-critical or open-ended functionality that we want to be able > > to extend. > > > > ARM is getting KVM and virtio-mmio support. It will be in a similar > > position soon. > > > > Virtio guest drivers have not been implemented widely. The Linux and > > Windows efforts are driven by the folks who were behind virtio from the > > start, but Solaris, FreeBSD, and others didn't really jump on the virtio > > bandwagon. > > > > Given this landscape, what is the advantage of doing a virtio-desktop? > > It will still need to fall back on ARM or x86 which is already being > > virtualized and emulated. > > > > Depending on how you see it we either have virtio-desktop already or, > > if not, I think the experience with virtio adoption suggests other > > hypervisors and guest OSes will not trip over themselves to implement > > virtio-desktop. > > > > What's the advantage over virtualizating an existing ARM or x86 platform > > and using virtio devices where appropriate? > > You don't get changing hardware for changing CPUs. I don't think it makes > sense to do a cross-arch virtio-desktop machine type. Different > architectures simply have different needs. > [Anup] Virtio-desktop does not rule-out archictecture needs. In fact, Virtio-desktop specfication can have architecture specific devices and architecture specific requirements. The most important point here is to have VM specification which mostly prefers Virtio devices. > > But check out the QEMU e500 machine. We have a fully device tree based > machine type in the kernel. QEMU drives it by generating a device tree for > devices it actually exposes on the fly. > > The big advantage we have here is that > > 1) We don't have to emulate all hardware real hardware emulates > 2) We're not restricted to emulate what real hardware emulates. PCI on > ARM anyone? > 3) Different CPU types can live on the same machine. This is something > that x86 is doing already. When you get a SoC, guests are usually > guaranteed a core <-> device correlation though. > > So overall, having a PV machine makes sense. Having the same common PV > machine standardized across different architectures does not make sense. > [Anup] Agreed. Virtio-desktop = Architecture dependent devices + Architecture requirements + Virtio devices. [Anup] Virtio-desktop specification will remain incomplete without incorporating architecture requirements. [Anup] I think it is possible to have a common Virtio-desktop specification which stresses on maximum use of Virtio devices and also includes architecture specific virtualization needs. > > > Alex > > > _______________________________________________ > kvmarm mailing list > kvm...@lists.cs.columbia.edu > https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm > --Anup
