Re: what should a virtio-mmio transport without a backend look like?

[Christopher Covington <cov@codeaurora.org>]

On 06/22/2013 06:51 AM, Peter Maydell wrote:
> On 21 June 2013 19:45, Christopher Covington <cov@codeaurora.org> wrote:
>> You were proposing to use a valid/existing MagicValue/Version/VendorID with a
>> special DeviceID that does nothing. I'm saying why not use a valid/existing
>> MagicValue/Version/VendorID/DeviceID with a special parameter setting, size=0,
>> that does nothing?

[...]

> Also, it's mixing a detail of the backend layer (what
> a zero-sized disk happens to look like) with the transport layer,
> which seems a bit ugly spec-wise.

I don't think that has to be the case. From what I understand of your
architecture, the device layer is completely opaque to the transport layer,
and the transport layer is immutable, but surely the device layer will at
least know how many transports are available? As long as that's true, can't
the device layer just create real devices and hook them up to transports, and
then create no-op devices and hook them up to any remaining transports?

> (Implementation wise I'm not crazy about it either since it would
> be way more complicated than saying "no backend? OK, RAZ/WI".)

(I thought virtio block devices were already implemented.)

Christopher

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