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Message-ID: <6f6293f105031207535938c687@mail.gmail.com>
Date: Sat, 12 Mar 2005 16:53:42 +0100
From: Felipe Alfaro Solana <felipe.alfaro@gmail.com>
Reply-To: Felipe Alfaro Solana <felipe.alfaro@gmail.com>
To: John Richard Moser <nigelenki@comcast.net>
Subject: Re: binary drivers and development
Cc: Peter Chubb <peter@chubb.wattle.id.au>, linux-kernel@vger.kernel.org
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On Thu, 10 Mar 2005 17:32:39 -0500, John Richard Moser
<nigelenki@comcast.net> wrote:
> CPL=3 scares me; context switches are expensive.  can they have direct
> hardware access?  I'm sure a security model to isolate user mode drivers
> could be in place. . .
> 
> . . . huh.  Xen seems to run Linux at CPL=3 and give direct hardware
> access, so I guess user mode drivers are possible *shrug*.  Linux isn't
> a microkernel though.

Xen hypervisor runs at Ring0, while the guest OSs it supports run at Ring1.
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