Critics on L4 (NOT Re: shared memory Beispiel?)

Espen Skoglund esk at
Wed Aug 31 14:17:33 CEST 2005

[Marcus Völp]
>> When those features are going to be implemented? 
> Fiasco implements IO Flexpages. Neither Redirectors nor Clans and
> Chiefs are currently implemented in Fiasco and probably never
> will. I cannot speak for plans regarding Pistachio.

Just some notes for L4Ka::Pistachio: Support for I/O flexpages have
been in the Pistachio CVS for some time now (I just updated the web
page to reflect this).  Clans & Chiefs are not part of the X2/V4
specification and will as such not be implemented.  Redirectors are
currently not implemented either.  This is more out of lazyness than
anything else, though.  Things are often implemented on a
whenever-we-need-it basis.  It's not terribly hard to add support for

>> Seems that there are so many differences between L4Ka::Pistachio
>> and Fiasco. Is there a stardard L4 specification?
> There is a standard L4 Specification: L4-V2 by Jochen Liedtke. Also
> there is the eXperimental specification you already found which is
> the defacto standard for L4-V4 kernels. The main difference between
> Pistachio and Fiasco is that the former implements L4-V4, the latter
> implements L4-V2 whereby some experimental features have been
> incorporated into Fiasco to better suite our user level software's
> needs. As you will see Fiasco already implements some parts of the
> L4-V4 specification. will give you a short introduction to the
different kernel APIs, and which implementations exist for them.


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