Re: [PATCH] Snapshot of shared page tables

From: Dave McCracken (dmccr@us.ibm.com)
Date: Wed Oct 02 2002 - 17:48:01 EST


--On Thursday, October 03, 2002 08:39:20 +1000 Paul Mackerras
<paulus@samba.org> wrote:

> Interesting. I notice that you are using the _PAGE_RW bit in the
> PMDs. Are you relying on the hardware to do anything with that bit,
> or is it only used by software?
>
> (If you are relying on the hardware to do something different when
> _PAGE_RW is clear in the PMD, then your approach isn't portable.)

Yes, I am relying on the hardware. I was under the impression that it was
pretty much universal that making the pmd read-only would make the hardware
treat all ptes under it as read-only. This came out of a discussion on
lkml last winter where this assertion was made.

Do you know of a page table-based architecture that doesn't have and honor
read-only protections at the pmd level?

Dave McCracken

======================================================================
Dave McCracken IBM Linux Base Kernel Team 1-512-838-3059
dmccr@us.ibm.com T/L 678-3059

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