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Re: vk_l4 -- CVS Setup

From: Farid Hajji
Subject: Re: vk_l4 -- CVS Setup
Date: Sun, 11 Nov 2001 01:07:32 +0100 (CET)

> > Even with two sub hurds, I could imagine running one sub-hurd on one
> > pager, and another sub-hurd on another pager.
> There can only be a single default pager for Mach.  This is
> effectively `outside of Hurd'.
Right. In L4, you can setup different pager threads, even recursively.
In Mach, you can have only one _default_ pager, but nothing prevents
you from setting up 2nd-level pagers backed up by one default pager.
Anyway, as you've correctly put it: it's "outside of Hurd".

> > Suppose that you provide nameservice via the Hurd. Now suppose that you
> > want to start the L4Linux server and have that server access the common
> > UVM-pager running on top of L4. Without hardcoding TIDs, the L4Linux
> > server bootstrapping code would need to ask the _Hurd's_ nameserver
> > (accessed via a well-known L4 TID belonging to, say, the Hurd's root
> > file server) for the TID of the common pager. 
> Again, the default pager is a property of Mach, not the Hurd.
This is exactly the reason why we need a Mach-like pager running on
top of L4, so that the Hurd or other OS personalities can draw memory
objects from it. It is not strictly Hurd-related, but a useful part of
a generic VK infrastructure.

As far as the Hurd is concerned, all that is important is that this
pager provides an interface "mostly" compatible to Mach's VM. That's
all I wanted to say here.

> > Put another way: Hurd-
> > independent requests would come from other parts (via L4) and will
> > need the Hurd's nameserver system to provide basic services. If you
> > look at it, it's _kind_of_ L4 doing an upcall to the Hurd OS personality.
> > This is terribly confusing, mostly because of mixing layers.
> I think you should take a look at the boot program; this has already
> solved this problem.


Farid Hajji -- Unix Systems and Network Admin | Phone: +49-2131-67-555
Broicherdorfstr. 83, D-41564 Kaarst, Germany  | address@hidden
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