"AW" == Adam 'WeirdArms' Wiggins awiggins@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. Phone: +61 2 9385 5156 / \ The University of NSW Fax: +61 2 9385 5995 _,--._* Sydney, Australia 2052 E-mail: G.Heiser@unsw.edu.au v http://www.cse.unsw.edu.au/~gernot PGP fingerprint = 94 1E B8 28 25 FD 7C 94 20 10 92 E5 0B FF 39 8F