linux-kernel - Re: linux page table

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Message-ID: <CAGDaZ_p5B-=Uf9PuHer9OiuUdAkRKy4aGt90T=FnKqE3M3sgwA@mail.gmail.com>
Date:	Sat, 1 Sep 2012 13:01:13 -0700
From:	Shentino <shentino@...il.com>
To:	Xin Tong <xerox.time.tech@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: linux page table

On Sat, Sep 1, 2012 at 12:30 PM, Xin Tong <xerox.time.tech@...il.com> wrote:
> When a process is created in Linux, corresponding page table is
> implemented. In the current x86 linux, the page table is a multi-level
> page table and CR3 points to the first level of the page table.  I
> have 2 questions.
>
> 1. is the value in CR3 virtual address or physical address ?

It's a physical address.  It points the CPU to it in physical memory.

More generally, all addresses in page tables, directories, etc are
physical addresses.

> 2. can the address of the first level of the page table during a
> process's lifetime change ?

This I don't know.

> 3. can two different processes have their CR3 being the same value
> even though they have different first level page tables ?

I'm not sure about this, but I think CR3 is actually bound to the
mm_struct and not the process.

Think about separate processes with the same address space, such as
multithreaded processes.

>
> Thanks
> --
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