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Re: Thoughts about the new X.2 spec...

From: Uwe Dannowski
Subject: Re: Thoughts about the new X.2 spec...
Date: Mon, 04 Feb 2002 10:50:28 +0100

Farid Hajji wrote:
> ... The mapping of IO pages to driver adress spaces is also incredibly
> useful and could improve performance a lot. ...

IO pages have been lurking around in L4 specifications at least since
Version 2, but have never been implemented before. They allow to securely
manage access to the x86' IO space. Read as: We now also include the x86'
second address space in L4's address space notion. Previously EVERY thread
was allowed to use in/out instructions.
To avoid misreading here, introducing IO pages DOES NOT improve performance.
It may improve security in that now you CAN control what address space's
threads can access what IO ports.


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