Re: [Xen-devel] Writes to guests' page table pages + mem_events

[Tim Deegan <tim@xxxxxxx>]

Hi, 

At 19:32 +0200 on 04 Nov (1383589938), Razvan Cojocaru wrote:
> looking at pages 6 and 7 of this document:
> 
> http://www-archive.xenproject.org/files/summit_3/XenSummit_Shadow2.pdf
> 
> I see that instructions writing to the page table pages of a guest are
> emulated by Xen.
> 
> Does this mean that, assuming that I make a page table page read-only, I
> will _not_ receive a mem_event if the guest tries to write to said page?

No, it doesn't.  That document describes the shadow-pagetable
mechanism, which is currently incompatible with mem_event (the
mem_event hypercalls check that the guest is using HAP).

Aravindh is looking into making (some parts of) mem_event work with
PV guests in shadow mode; that will prbably use a quite different
mechanims, closer to how log-dirty mode works.


Cheers,

Tim.

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