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Re: [Xen-devel] Xen Roadmap proposal and Mini-OS C library

To: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] Xen Roadmap proposal and Mini-OS C library
From: ramsdell@xxxxxxxxx (John D. Ramsdell)
Date: 13 Jul 2006 08:06:40 -0400
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Thank you for your detailed report.

> As a user space application, Qemu can't run in the stub domain
> directly, but requires an operating system kernel. The neatest way of
> doing this would be to link qemu against `minios', which is
> effectively a library operating system for just this purpose. Since
> minios makes use of a broad range of libc calls, it is likely that
> minios will take some time to reach the required level of support. In
> the meantime, we can just use a xen linux kernel, with a minimal
> config to keep the size down. Since protection between user space and
> the kernel is irrelevant in the context of running qemu as the sole
> application, we could optimize performance by running user-space at
> the same privilege level as the kernel, effectively turning system
> calls into plain jmp instructions into the kernel followed by a ret to
> return.

Your assessment of Mini-OS's C library support is too bleak.  In an
effort to ease the task of writing applications that run in Mini-OS, I
ported a Lua interpreter to it <http://www.lua.org>.  The standard Lua
interpreter is patched so that it does not use floating point
operations, and then linked against the newlib C library
<http://sources.redhat.com/newlib/>, a library intended for use on
embedded systems.  To make a bootable VM, all of the sources,
including the Mini-OS sources, are compiled with a cross-compiler with
a target of i386-elf.  The Mini-OS Makefile provides hooks to make
this all possible.  Gregor has a copy of sources.


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