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From: | Frank Ch. Eigler |
Subject: | Re: [Qemu-devel] [PATCH] KVM: Add wrapper script around QEMU to test kernels |
Date: | Mon, 07 Nov 2011 15:03:00 -0500 |
User-agent: | Gnus/5.1008 (Gnus v5.10.8) Emacs/21.4 (gnu/linux) |
Ingo Molnar <address@hidden> 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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