Re: Tracking changes to writable page tables

[Jacob Gorm Hansen <jacobg@diku.dk>]

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