Mark Williamson wrote:

Also, I suppose you will wish to prevent covert channels between
domains, e.g. domains communicating using various timing attacks (I move
the disk head to the other end of the disk if I wish to tell you
something), or by allocating/freeing certains parts of memory.
How much will you need to dumb down the VMs view of what is going on in
the machine to achieve this (not expose real time information, not
expose real page tables), and how much of a VMM will there be left when
you are done?

Well domains are not aware of each other's memory usage, so I wouldn't have thought that allocation / exposing real page tables would matter. (Except dom0 can of course see everything if it wants).

Information about other domains' memory usage is leaked via the
hardware->physical mapping.

Timing related attacks are somewhat trickier to eliminate covert channels in, although some randomisation can limit the bandwidth.

Eliminating covert channels is completely infeasible. I don't see any
value in aiming for this. It's not a useful security property in most
circumstances.
--
David Hopwood <david.nospam.hopwood@xxxxxxxxxxxxxxxx>
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