FPU state management in L4Fiasco.OC program

Adam Lackorzynski adam at os.inf.tu-dresden.de
Tue Apr 17 00:25:58 CEST 2012

On Fri Apr 13, 2012 at 13:33:54 -0500, Mai, Haohui wrote:
> Adam,
> Thanks for your clarification.
> One thing that I'm not still quite clear is that how to manage FPU context
> in my settings.
> The main challenge here is that to keep track the "current" pointer
> (similar to the current pointer in L4Linux) -- otherwise it's difficult to
> save the FPU context.
> My OS only handles page faults and syscalls, and delegates scheduling
> processes to L4 completely.
> Handling page faults and syscalls is easy in the sense that the IPC
> messages have complete information.
> However, It's not immediately clear to me that how to keep track of
> "current" pointer and to save / restore FPU context.
> Do you have any comments on this one? I appreciate your help.

Ok, then the question actually is why your user processes are running as
aliens at all. Receiving page-faults and other exceptions does not
depend on being an alien. This also works without it. Then the kernel
would just handle the FPU transparently for the threads and your handler
thread does not need to care about that.

Adam                 adam at os.inf.tu-dresden.de
  Lackorzynski         http://os.inf.tu-dresden.de/~adam/

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