Sharing I/O Memory

Adam Lackorzynski adam at
Mon Jan 30 10:13:23 CET 2012


On Fri Jan 27, 2012 at 18:15:46 -0800, Wesley Miaw wrote:
> I have an L4 process requesting access to a large chunk (512MB) of
> physical RAM using l4sigma0_map_iomem(). I am not using l4sigma0_map_mem()
> because Fiasco is running in a different partition of physical RAM.
> I would like to then grant full read/write access to the same memory to a
> second L4 process, but I'm not sure how to do that. I believe from looking
> at the sigma0 code that any memory, I/O or RAM, can only be allocated to
> one L4 process at a time.

Yes, any page or port can only be given to one client.
> It also doesn't look like clans have anything to do with this, other than
> the possibility of creating some shared memory for an IPC. But that's not
> really what I want to do, I want both L4 processes to directly access the
> memory. Is there some way to accomplish this?

Common practice is to have a roottask which handles allocation of memory
in the desired ways. With 'directly access' you mean that no roottask (or
similar) can revoke access to the memory?

Adam                 adam at

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