[libvirt] [PATCH 10/18] qemu: Support filesystem model=virtio-{non-}transitional

[Andrea Bolognani]

On Fri, 2019-01-18 at 11:44 +0000, Daniel P. Berrangé wrote:
> For QEMU the <filesystem> element currently implies the 9p filesystem
> passthrough impl.
> 
> We already have a need to reuse it for USB-MTP filesystem sharing,
> and quite soon we'll have to support virtio-fs too. The virtio-fs
> module is essentially fuse-over-virtio IIUC.  In fact I wonder why
> we're not just calling that device virtio-fuse to make it explicit !
> 
> Anyway the point is that model=virtio-transitional is potentially
> ambiguous, depending on how we intend to deal with this.
> 
> I was at first thinking of  model="virtio-9p|virtio-fs|usb-mtp"
> to deal with the existing issue, but you're proposing using model
> already.
> 
> I'm a little mixed about how to best dovetail with the transitional
> stuff. We could use 'model' stuff but expand it:
> 
>    virtio-9p
>    virtio-9p-transitional
>    virtio-9p-non-transitional
>    virtio-fs
>    usb-mtp
> 
> IIUC, we don't need a -transitional/-non-transitional variant for
> virtio-fs since it will be a modern device only - same as with
> virtio-gpu.
> 
> Or we could do things different and invert something like a 'protocol'
> concept for the filesystem. 
> 
>   <filesystem type='mount'>
>      <target dir="foo" protocol="9p|mtp|fuse"/>
>   </filesystem>

Welp, I wish I'd re-read this message before reviewing the previous
patch :)

It looks to me like 'model' as used by Cole and and 'protocol' as
suggested by you are basically complementary, so having both of
them seems pretty reasonable from a quick look.

-- 
Andrea Bolognani / Red Hat / Virtualization