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Re: [Xen-devel] Xen architecture

from [Ian Pratt]

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To:	"Woloszynski, Charles" <charles.woloszynski@xxxxxxxxxxx>
Subject:	Re: [Xen-devel] Xen architecture
From:	Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>
Date:	Fri, 20 Feb 2004 00:15:06 +0000
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> So, the two questions are:
> (1)  Can a GuestOS ever bypass the Xen boundaries?  

We can't guarantee there aren't bugs in Xen, but that's certainly
the design goal.  Maintaining isolation between guests is
paramount. The trick is doing it with good performance. That's
what makes Xen fun to work on ;-)

> (2)  How big (in lines of code) is the subsystem in Xen that enforces this?

The hard/clever part is memory protection. That's mostly
implemented in common/memory.c which is 1100 lines. The whole of
Xen is 20 times that, but there's a lot of hardware
initialisation code etc that isn't "guest facing". 

Ian



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