From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jeremy Fitzhardinge <jeremy@goop.org>
Subject: Re: Xeno Linux never pins L1 tables ?
Date: Tue, 16 Oct 2007 12:57:45 -0700
Message-ID: <471517B9.1040102@goop.org>
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To: Satya <satyakiran@gmail.com>
Cc: Xen-devel <xen-devel@lists.xensource.com>
List-Id: xen-devel@lists.xenproject.org

Satya wrote:
> I'm developing my own 32-bit (no PAE) paravirtualized kernel for xen
> with Mini-OS as a starting point. I am currently working on process
> page table support (equivalent of arch/i386/mm/pgtable-xen.c) and
> mostly following Linux for the moment. I noticed that linux-2.6.18-xen
> never pins an L1 table (a pte), yet __pgd_pin() walks the page
> directory and gives up write access on the kernel mappings of pte
> pages and only pins the pgd page. How do set_pte() and set_pte_at()
> macros work if they are writing directly to the page table entires ?
> do we fault in the kernel to handle this ?! 

Pinning the top level of a pagetable implicitly pins all the lower
levels, so they are all pinned.

    J