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Date: Wed, 21 Dec 2016 07:43:48 -0800
From: Christoph Hellwig <hch@infradead.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>,
        Roman Kagan <rkagan@virtuozzo.com>,
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        "H. Peter Anvin" <hpa@zytor.com>, devel@linuxdriverproject.org,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 12/15] hyperv: move VMBus connection ids to uapi
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On Wed, Dec 21, 2016 at 04:39:18PM +0100, Paolo Bonzini wrote:
> That said, there are precedents in using UAPI this way for PV
> interfaces.  See for example include/uapi/linux/virtio*.h and
> arch/x86/include/uapi/asm/kvm_para.h.

We have all kinds of historical examples, but most of them turned
into a major pain sooner or later - my favourite example are the
SCSI protocol headers.

Protocols needs to stay compatible on the (virtual) wire, but not
on the language level.  Locking us into the strict UABI policies
for them just make someone life horrible further down the road.