Sharing I/O Memory

Adam Lackorzynski adam at
Tue Jan 31 21:55:38 CET 2012


On Mon Jan 30, 2012 at 19:35:45 -0000, Wesley Miaw wrote:
> >> I couldn't find any way to revoke access once granted via sigma0. Or
> >> for a L4 userland process to "put back" the memory it has previous
> >> requested access to.
> >
> > Processes can unmap their memory themselves, or those inbetween. Just
> > not sigma0 because that's not its task. io is handling everything non-ram
> > for multiple clients etc. I'd think of the normal side as a device which
> > has some (big) MMIO and handle it that way on the secure side. Why would
> > you like to get rid of the memory again?
> I thought if I had a process release its memory then another process could
> be granted it. And so I could map and then unmap for reach request. But it
> sounds like I should look into the io server a bit more, or re-read
> through how moe can configure things.

Generally multiple tasks can have access to the same memory, be it RAM
or devince memory does not matter. Doing map/unmap operations for each
request also sounds expensive to do. I think io is the one to look into,
moe has no business with non-ram memory.

Adam                 adam at

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