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Re: [Xen-devel] Tracking changes to writable page tables

To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Tracking changes to writable page tables
From: Jacob Gorm Hansen <jacobg@xxxxxxx>
Date: Sun, 15 May 2005 01:30:50 -0700
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Ian Pratt wrote:

I wander if we should steal one of the OS bits in the PTE to
differentiate writable pagetable mappings? You could then take a normal
RO fault, set the bit, and then retry to have Xen do pagetable the work.

This would arguably be cleaner, though we've been reluctant to steal OS
bits just incase there's some OS out there that uses them all.

Yes, that would also be a solution, though it is a little nasty to steal
the AVL bits.

Alternatively, I can just add the tracking to set_pte(), assuming that
all updates come through there, but that will probably slow down page
table updates a bit, even while not checkpointing the kernel.

Jacob


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