Re: QEMU PIC indirection patch for in-kernel APIC work

Avi Kivity
2007-04-05T09:58:30Z

Ingo Molnar wrote:
> so right now the only option for a clean codebase is the KVM in-kernel
> code.

I strongly disagree with this. Bad code in userspace is not an excuse
for shoving stuff into the kernel, where maintaining it is much more
expensive, and the cause of a mistake can be system crashes and data
loss, affecting unrelated processes. If we move something into the
kernel, we'd better have a really good reason for it.

Qemu code _is_ crufty. We can do one of three things:
1. live with it
2. fork it and clean it up
3. clean it up incrementally and merge it upstream

Currently we're doing (1). You're suggesting a variant of (2), fork
plus move into the kernel. The right thing to do IMO is (3), but I
don't see anybody volunteering. Qemu picked up additional committers
recently and I believe they would be receptive to cleanups.

[In the *pic/pit case, we have other reasons to push things into the
kernel. But "this code is crap, let's rewrite it in the kernel" is not
a justification I'll accept. I'd be much happier if we could quantify
these other reasons.]

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