From: Jiri Kosina <jkosina@suse.cz>
To: Xin Tong <xerox.time.tech@gmail.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: linux page table
Date: Sun, 2 Sep 2012 10:10:41 +0200 (CEST) [thread overview]
Message-ID: <alpine.LRH.2.00.1209021005090.22050@twin.jikos.cz> (raw)
In-Reply-To: <CALKntY00bG_wVpOGM_L9ENLqROgSO_TttXJeTkgkERdtpnwi_A@mail.gmail.com>
On Sat, 1 Sep 2012, Xin Tong 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 ?
Physical, otherwise you will have chicken-egg problem.
> 2. can the address of the first level of the page table during a
> process's lifetime change ?
In theory it would be possible to implement. But I don't see a scenario
when it might be useful.
> 3. can two different processes have their CR3 being the same value
> even though they have different first level page tables ?
Yes, if they are created by clone(CLONE_VM). In such case they share the
same mm_struct, and therefore mm_struct->pgd (which is exactly what is
loaded into cr3 in switch_mm()) is the same.
LKML is however very inappropriate list for such questions. Please ask on
kernelnewbies list next time.
--
Jiri Kosina
SUSE Labs
next prev parent reply other threads:[~2012-09-02 8:10 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-01 19:30 linux page table Xin Tong
2012-09-01 20:01 ` Shentino
2012-09-01 20:12 ` Xin Tong
2012-09-02 8:10 ` Jiri Kosina [this message]
2012-09-02 15:56 ` Xin Tong
2012-09-02 18:26 ` Jiri Kosina
2012-09-04 8:48 ` Cong Wang
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