Re: [Qemu-devel] [PATCH] KVM: Add wrapper script around QEMU to test kernels

Frank Ch. Eigler
2011-11-07T20:03:50Z

Ingo Molnar <mingo@elte.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