Question about memory management in L4 Fiasco O.C + L4re

Mahdi Aichouch foxmehdi at gmail.com
Fri Jul 17 10:36:35 CEST 2015


Hello Adam,

The memory regions are exclusive. Specifying exactly which physical
> memory an L4Linux is getting is currently not possible but I guess
> you're using the numbers just as an example?


Yes, I am giving these numbers as an example.
However, is it possible to know what are the start address and the end address
of a physical memory partition allocated to a L4Linux instance?

The memory is completely mapped initially, so no page fault should
> happen. As probably nobody will take it away again it should also stay
> like this.

Does this apply also to user-level programs executed on top of L4Linux.

You can put showpfexc=1 on the cmdline to see any in-kernel page fault.
>
There shouldn't be any (except in the outside wrapper code as I see
> which can be changed by launching L4Linux with the eager_map flag).

Could please give some explanation about what is the wrapper code? And
Where to set the "eager_map flag" option?

Thank you very much for your answer!

Best regards,

Mahdi



On Wed, Jul 15, 2015 at 11:53 AM, Mahdi Aichouch <foxmehdi at gmail.com> wrote:

> Hello,
>
> I have some questions concerning memory management in Fiasco O.C  + L4re.
>
> I would like to test two L4Linux instances, and for each L4Linux
> instance I want to reserve one static fixed physical memory partition.
>
> For instance, one 128MB for the first L4Linux and one 128MB for the second.
>
> Knowing that Fiasco O.C. uses "on demand paging" to allocate pages for
> user tasks, is it possible that each partition of L4Linux could be
> allocated
> a static physical memory region composed of contiguous physical frames.
>
> For instance, one memory region starting from 128MB to 256MB for the first
> L4Linux,
> and second memory region from 256MB to 512MB for the second L4Linux.
> Each memory region is allocated exclusively to one L4Linux instance.
>
> I would like to know if it is possible to load all the code + data of a
> L4Linux instance
> into its reserved memory partition, so no page fault will be encountered
> during runtime.
>
> Is it possible to tell me if these above operations could be realized in
> Fiasco O.C and L4re?
>
> If the answer is yes, is it possible to tell me what are the objects that
> should be used or
> adapted in order to implement these?
>
> What are the issues that I should pay attention to?
>
> Many thanks in advance for your answer.
>
> Best regards,
>
> Mahdi
>
>
>
>
>
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