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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH 0/6] Multi-level page tables and userland
	mapping fixes.
Date: Sun, 28 Feb 2010 23:23:53 +0000
References: <cover.1265933756.git.rth@twiddle.net>
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To: qemu-devel@nongnu.org
Cc: Richard Henderson <rth@twiddle.net>

> Which brings us to the problem of exec.c and the address spaces therein.
> First, there was the fact that TARGET_PHYS_ADDR_SPACE_BITS was constrained
> to be no larger than 32 (with a partial hack for Alpha to extend this to
> 42 bits).  Second, that this physical address space value was applied to
> virtual addresses via page_find.

On further investigation (I missed this the first time round) it gets worse 
than that :-(  While userspace emulation uses PageDesc to describe virtual 
pages, system emulation uses it to track physical pages. This probably helps 
explain why the existing code is so confused.

I'm not sure why we have separate l1_map and l1_phys_map. My guess is it's an 
attempt to save memory, on the theory that typically only a small faction of 
ram will be used to hold code.
 
> This patch series untangles this somewhat.

Looks like a fairly good start, however they're missing a Signed-off-by.

Paul