[Rust-VMM] Including a virtio-bindings crate in rust-vmm

[Liu Jiang]

> On May 8, 2019, at 10:17 PM, Sergio Lopez <slp at redhat.com <mailto:slp at redhat.com>> wrote:
> 
> 
> Paolo Bonzini <pbonzini at redhat.com <mailto:pbonzini at redhat.com>> writes:
> 
>> On 08/05/19 07:18, Sergio Lopez wrote:
>>> Hi,
>>> 
>>> I think it'd be useful having a crate providing virtio bindgen-generated
>>> bindings, similar to Firecracker's virtio_gen. I wrote one that provides
>>> the same functionality, but with multiple versions mapped as features,
>>> as kvm-bindings does:
>>> 
>>> https://git.sinrega.org/slp/virtio-bindings <https://git.sinrega.org/slp/virtio-bindings>
>>> 
>>> Do you think we could make this a project under rust-vmm's umbrella?
>>> 
>>> Thanks,
>> 
>> Yes, I think so!  However, what is the reason to have anything but the
>> last version?  Headers from a newer kernel should be
>> backwards-compatible with code written for an older kernel.
> 
> The main reason is for that is allowing crate users to be able to do
> strict size checks on structs.
> 
> As an example, virtio_blk_config was extended from 4.14 to 5.0 with new
> fields. This structure may come as the payload a VhostUserConfig
> message, and while you are able to just use the latest version and
> accept any payload the same size or smaller, I think some users may want
> to be more strict and just allow the expected size.
> 
> Given that the cost of maintaining the bindings is very small, I think
> that's a use case we can afford supporting (and I volunteer for doing so
> :-).
A hypervisor may support multiple kernel versions. So how about defining multiple data structure for different kernel versions?
BTW, the auto-generated code has some useless code with poor readability.
It would be appreciated to manually maintain a beatified version:)

> 
> Thanks,
> Sergio.
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