Date: Sun, 26 Aug 2001 10:33:31 -0700 From: Mike Smith <msmith@freebsd.org> To: Ronald G Minnich <rminnich@lanl.gov> Cc: Mike Smith <msmith@FreeBSD.ORG>, djohnson <johnson@faradayco.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: PCI Enumeration Message-ID: <200108261733.f7QHXVr00963@mass.dis.org> In-Reply-To: Your message of "Sun, 26 Aug 2001 10:55:59 MDT." <Pine.LNX.4.33.0108261055240.10092-100000@snaresland.acl.lanl.gov>
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> On Sat, 25 Aug 2001, Mike Smith wrote:
>
> > I/O space is easy, but memory space is hard. Userspace access to
> > physical memory is a big no-no in the *nix world.
>
> I want to disagree just a bit. If you look at myrinet, or the many fpga
> cards, it's the standard modus operandi. You have to do it that way.
You're not disagreeing; you're talking at cross purposes.
Direct userspace access to physical memory is bad.
The ability for user processes to access *specific* physical memory via
kernel-owned protection paths is often necessary to meet specific
performance goals, or to overcome lame hardware designs.
--
... every activity meets with opposition, everyone who acts has his
rivals and unfortunately opponents also. But not because people want
to be opponents, rather because the tasks and relationships force
people to take different points of view. [Dr. Fritz Todt]
V I C T O R Y N O T V E N G E A N C E
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