L4 Mapping question

[Gernot Heiser]

>>>>> "AW" == Adam 'WeirdArms' Wiggins <awiggins at cse.unsw.edu.au> writes:

AW> On Mon, 22 Feb 1999, Robert Kaiser wrote:
>> Hi all,
>> 
>> I have a question regarding mapping in L4:
>> 
>> I read in the L4 reference manual that Sigma0 maps each page
>> only once. It does allow multiple mappings of a page to the
>> same address space (i.e. task), but it does not allow multiple
>> mappings to different tasks.

AW> 	A related question here. Is there any particular reason/need for
AW> sigma zero to be a once off pager? Why not have an inteligent resource
AW> manager for sigma zero?

Separation of policy and mechanism. It's the OS personality's business
to sort this out, not the kernel's.

Gernot

Note that in a politically correct L4 (which the MIPS one isn't)
\sigma_0 is not part of the kernel but runs at user level, and is bound
to the kernel at boot image creation time (and can easily be exchanged
for something different). However, if you're the one who's building the
boot image, you can just as well rebuild the kernel with a different
\sigma_0, so this isn't much of an issue.

--
Gernot Heiser                ,--_|\   School of Computer Sci. & Engin.
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