Re: [kvm-devel] [PATCH 3/3] virtio PCI device

Zachary Amsden
2007-11-21T18:19:42Z

On Wed, 2007-11-21 at 09:13 +0200, Avi Kivity wrote:

> Where the device is implemented is an implementation detail that should
> be hidden from the guest, isn't that one of the strengths of
> virtualization? Two examples: a file-based block device implemented in
> qemu gives you fancy file formats with encryption and compression, while
> the same device implemented in the kernel gives you a low-overhead path
> directly to a zillion-disk SAN volume. Or a user-level network device
> capable of running with the slirp stack and no permissions vs. the
> kernel device running copyless most of the time and using a dma engine
> for the rest but requiring you to be good friends with the admin.
>
> The user should expect zero reconfigurations moving a VM from one model
> to the other.

I think that is pretty insightful, and indeed, is probably the only
reason we would ever consider using a virtio based driver.

But is this really a virtualization problem, and is virtio the right
place to solve it? Doesn't I/O hotplug with multipathing or NIC teaming
provide the same infrastructure in a way that is useful in more than
just a virtualization context?

Zach