Re: [Xen-devel] Entry points for updates to shadow PTs

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 00:15 -0400 on 02 May (1209687305), Mike Sun wrote:
> In which places can shadow PTEs be changed and/or where is the best
> place for me to check to see if I must remark them read-only for my
> purposes?  Maybe in a low level function like "shadow_set_l1e"?

Shadow PTEs are calculated from guest PTEs in _sh_propagate(): anywhere
that we write a shadow entry, it should have come from a call to one of
the propagate_from_guest() functions, which all end up in _sh_propagate().

There's already a clause in that function to remove the _PAGE_RW bit if
the target page hasn't been marked dirty and log-dirty mode is enabled.
Extending that should be enough.

The tricky part, I would have thought, is finding all the places where
guest memory is written without going via the shadow pagetables.

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

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