hello and question from a l4 beginner

Espen Skoglund esk at ira.uka.de
Thu Jan 26 16:37:37 CET 2006

[Xavier Grave]
>>> Can I avoid this ? I have to ask to map it to sigma0 ?
>> You can't map anything *to* sigma0.  Sigma0 automagically owns all
>> memory.  But yes, you have to map memory from sigma0 to the root
>> task.

> Ok, how can I do this so ?

Sigma0 will by default be the pager of the root task.  Sigma0 will
resolve any pagegaults and map the pages to the root task using the
smallest possible page size.

You might want to request the pages explicitly from sigma0 (see
include/l4/sigma0.h) so that you can have larger page sizes mapped to
you.  Also, certain special memory regions (e.g., device memory) can
not be pagefaulted into the root task.  They have to be requested

Also remember that sigma0 will refuse to give out pages to the root
task if they have been allocated to something else.

>> Why would you want to avoid that?

> What I want to avoid is the page fault. Sorry for my bad english. My
> ideas are not very clear on l4 and if you add the filter of my poor
> english....

The initial pagefault(s) are difficult to avoid.  You can however
request sigma0 to remap pages.  This also works if you request sigma0
to remap the memory using larger page sizes.


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