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[Xen-devel] Re: [RFC, PATCH 5/24] i386 Vmi code patching

Chris Wright wrote:
* Andi Kleen (ak@xxxxxxx) wrote:
The disassembly stuff indeed doesn't look like something
that belongs in the kernel.

Agree that. It should be done prior to kernel booting, invisible to the kernel itself. I'm working on it, but there is still a lot to do.

Strongly agreed.  The strict ABI requirements put forth here are not
in-line with Linux, IMO.  I think source compatibility is the limit of
reasonable, and any ROM code be in-tree if something like this were to
be viable upstream.

Strongly disagree. Without an ABI, you don't have binary compatibility. Without binary compatibility, you have no way to inline any hypervisor code into the kernel. And this is key for performance. The ROM code is being phased out.

Is it the strictness of the ABI that is the problem? I don't like constraining the native register values any much either, but it was the expedient thing to do. The ABI can be relaxed quite a bit, but it has to be there.

The idea of in-tree ROM code doesn't make sense. The entire point of this layer of code is that it is modular, and specific to the hypervisor, not the kernel. Once you lift the shroud and combine the two layers, you have lost all of the benefit that it was supposed to provide.


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