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Re: [Xen-devel] What is machine address?

To: "Ronald G. Minnich" <rminnich@xxxxxxxx>
Subject: Re: [Xen-devel] What is machine address?
From: Kip Macy <kmacy@xxxxxxxxxxxxxxx>
Date: Thu, 16 Sep 2004 11:33:19 -0700 (PDT)
Cc: Steven Hand <Steven.Hand@xxxxxxxxxxxx>, Chengyuan Li <chengyuanli@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxxx
Delivery-date: Thu, 16 Sep 2004 19:33:26 +0100
Envelope-to: Steven.Hand@xxxxxxxxxxxx
In-reply-to: <Pine.LNX.4.58.0409161112500.11464@xxxxxxxxxxxxxxxx>
References: <E1C7rcU-0004mb-00@xxxxxxxxxxxxxxxxx> <Pine.LNX.4.58.0409161112500.11464@xxxxxxxxxxxxxxxx>
How does Plan 9 efficiently handle a large number fragmented memory
ranges? FreeBSD can do it, but not well enough to eliminate the PA/MA
dichotomy?

                        -Kip

On Thu, 16 Sep 2004, Ronald G. Minnich wrote:

>
> MA = machine address
> PA = physical address
> VA = virtual
> On Thu, 16 Sep 2004, Steven Hand wrote:
>
> > Physical address = address of a piece of memory used by a guest operating
> > system (starting at 0 and going up to the amount of memory you have in
> > that particular virtual machine).
>
> On real machines, PAs == the real hardware.
>
> On Xen domains, PAs == not real hardware.
> Xen actually virtualize physical addresses, so although the PA range in an
> OS may be linear and contiguous, the underlying MAs are not.
>
> At some point I want to fix up Plan 9 to ignore PAs entirely and just VA
> and MA, but that's for later. The concept of a PA has no real meaning
> anyway at this point, so I see no reason to deal with it.
>
> ron
>
>
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