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Re: [Qemu-devel] [RFC] Virtio-desktop: Virtio-based virtual desktop


From: Anup Patel
Subject: Re: [Qemu-devel] [RFC] Virtio-desktop: Virtio-based virtual desktop
Date: Thu, 24 Jan 2013 18:38:25 +0530

On 24 January 2013 14:55, Stefan Hajnoczi <address@hidden> 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.
[Anup] I think other OSes will be motivated to added Virtio drivers if there
exists some think like Virtio-desktop specification that is being emulated by
many hypervisors.


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.
[Anup] Virtio-desktop stresses on having minimum architecture dependent
devices. Any improvements or additions in Virtio-desktop will be available
to other architectures.
 

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.
[Anup] I believe Virtio adoption will increase by having a concrete
Virtio-desktop specification and without it Virtio devices are just another
way of para-virtualization. In fact, having Virtio-desktop support for an OS
will enable it to run under different hypervisors.


What's the advantage over virtualizating an existing ARM or x86 platform
and using virtio devices where appropriate?
[Anup] With Virtio-desktop, many platforms can share lot of common
code mostly in-form of Virtio devices. We already drivers for most
Virtio devices in the mainline Linux kernel. The only missing devices are
Virtio-fb, Virtio-input, and Virtio-power from Virtio-desktop perspective.
[Anup] Further, Virtio is interface independent which means a Virtio device
can be a MMIO-based device or PCI-based device or some other form.
[Anup] Most proprietary hypervisors and Xen already have para-virtualized
devices which are similar to Virtio devices. In fact, we have wide variety of
approaches in para-virtualization. We can think of Virtio and Virtio-desktop as
an attempt to standardize para-virtualization in an architecture independent and
hypervisor independent way. Of-course, implementation and performance of
Virtio devices will vary under different hypervisors.
 

Stefan

--Anup

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