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Message-ID: <y0mpqh3og3v.fsf@fche.csb>
Date: Mon, 07 Nov 2011 15:03:00 -0500
From: fche@...hat.com (Frank Ch. Eigler)
To: Ingo Molnar <mingo@...e.hu>
Cc: Vince Weaver <vince@...ter.net>,
Pekka Enberg <penberg@...helsinki.fi>,
"Ted Ts'o" <tytso@....edu>, Pekka Enberg <penberg@...nel.org>,
Anthony Liguori <anthony@...emonkey.ws>,
Avi Kivity <avi@...hat.com>,
"kvm@...r.kernel.org list" <kvm@...r.kernel.org>,
"linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
qemu-devel Developers <qemu-devel@...gnu.org>,
Alexander Graf <agraf@...e.de>,
Blue Swirl <blauwirbel@...il.com>,
=?iso-8859-1?Q?Am=E9rico?= Wang
<xiyou.wangcong@...il.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [Qemu-devel] [PATCH] KVM: Add wrapper script around QEMU to test kernels
Ingo Molnar <mingo@...e.hu> writes:
> [...]
>> It's problem enough that there's no way to know what version of the
>> perf_event abi you are running against and we have to guess based
>> on kernel version. This gets "fun" because all of the vendors have
>> backported seemingly random chunks of perf_event code to their
>> older kernels.
>
> The ABI design allows for that kind of flexible extensibility, and
> it's one of its major advantages.
>
> What we *cannot* protect against is you relying on obscure details of
> the ABI [...]
Is there some documentation that clearly spells out which parts of the
perf syscall userspace ABI are "obscure" and thus presumably
changeable?
> [...] The usual ABI rules also apply: we'll revert everything that
> breaks the ABI - but for that you need to report it *in time* [...]
If the ABI is so great in its flexible extensibility, how come it
can't be flexibly extended without having to passing the burden of
compatibility testing & reversion-yawping to someone else?
- FChE
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