NOVA: remote revoke

[Udo Steinberg]

On Mon, 23 Jul 2012 14:19:31 +0200 Norman Feske (NF) wrote:

NF> > So you'd need something like a "directed revoke" feature. We had
NF> > something like that in Fiasco-V2, where you could do an "unmap
NF> > without self" and additionally specify a task number. Only child
NF> > mappings for that task and its children would be removed. In the
NF> > NOVA case, you'd specify a PD capability instead of a task number.
NF> 
NF> that's what I'm after.

There are some subtle corner cases possible if revoke gets preempted. One is
that if you do a revoke (range, PD-cap), the range obviously cannot go away,
but the PD-cap can. This means if you do a directed revoke by specifying a
PD-cap, and the PD-cap (or the PD) goes away in the middle of a preempted
revoke, the remainder of the revoke would fail to look up the PD and do a
full revoke of the range instead.

Alternatively you'd have to hold onto the PD-cap while a revoke with that
PD-cap is ongoing, which is hardly any better.

Cheers,
Udo
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