RE: [PATCH 12/15] hyperv: move VMBus connection ids to uapi

[KY Srinivasan]

> -----Original Message-----
> From: Stephen Hemminger [mailto:stephen@xxxxxxxxxxxxxxxxxx]
> Sent: Wednesday, December 21, 2016 10:03 AM
> To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>; Roman Kagan
> <rkagan@xxxxxxxxxxxxx>; Radim Krčmář <rkrcmar@xxxxxxxxxx>; KY
> Srinivasan <kys@xxxxxxxxxxxxx>; Vitaly Kuznetsov
> <vkuznets@xxxxxxxxxx>; kvm@xxxxxxxxxxxxxxx; Denis V . Lunev
> <den@xxxxxxxxxx>; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>;
> x86@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Ingo Molnar
> <mingo@xxxxxxxxxx>; H. Peter Anvin <hpa@xxxxxxxxx>;
> devel@xxxxxxxxxxxxxxxxxxxxxx; Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Subject: Re: [PATCH 12/15] hyperv: move VMBus connection ids to uapi
> 
> On Wed, 21 Dec 2016 09:58:36 -0800
> Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:
> 
> > On Wed, Dec 21, 2016 at 09:50:49AM -0800, Stephen Hemminger wrote:
> > > Lastly, there is licensing issues on headers. It would be good to have any
> > > userspace ABI headers licensed with a more liberal license so that BSD
> and DPDK drivers
> > > could use them directly. Right now each one reinvents.
> >
> > Microsoft could easily solves this problem by offering a suitably
> > liberally licensed header documenting the full HyperV guest protocol
> > that Linux and other projects could use.
> 
> The issue is if same header file mixes kernel and userspace API stuff.
> 
> Once the files are arranged right, I will submit trivial change to comments
> to indicate the liberal licensing of userspace API headers.

Let us take this one step at a time. I know for a fact that not all the guest host
protocols on Hyper-V are guaranteed to be stable. Some of the protocols are part of
the published MSFT standards such RNDIS and these obviously are guaranteed to be
stable. For the rest it is less clear. The fact that we need to ensure compatibility of existing
Windows guests tells me that any host side changes will be versioned and the hosts will always
support older guests.

I would like to minimize what we include in the uapi header; especially when MSFT has made no guarantees
with regards how  they may be evolved. I will also work on getting some clarity on both stability and
under what license we would expose the uapi header.

Regards,

K. Y