Using Fiasco L4re APIs

[Norman Feske]

Hi Daniel,

> As far as design choice, I think you need both.  When you can use an 
> affinity mask for a set of threads that belong to a single CPU session, 
> then setting this mask through the CPU session works.  However, lets say 
> you want to explicitly define each individual mapping of thread to 
> core.  In this case you either need to be able to define the affinity 
> from the thread, or some how build a map of threads-to-affinity in the 
> CPU session.  The latter could be cleaner, but less conventional.

What if one program would create multiple CPU sessions and specify the
CPU session for each thread as constructor argument of the 'Thread'
class? In the extreme case, each thread could be created via a distinct
CPU session using a different affinity. The program would express its
desired affinity for each CPU session as session argument. The parent
then has the option to change the affinity when forwarding the session
request towards Genode's core. This would be a quite powerful mechanism
to assign any subsystem to arbitrary sets of CPUs without letting the
subsystem know about it.

Currently, the 'Thread_base' implementation always uses the CPU session
of 'Genode::env()->cpu_session()'. However, the replacement of this
hard-wired policy by a construction argument would be a sensible way to
enable the binding of threads to manually created CPU sessions.

> I did try to include the l4sys headers in my genode program, but it sort 
> of blew up - it found the headers but not things like L4_PAGESHIFT.

Normally, this shouldn't be a problem. Can you give the following
program a try?

base-foc/src/test/headers/test.cc:

  namespace Fiasco {
  #include <l4/sys/types.h>
  }

  #include <base/printf.h>

  int main(int argc, char **argv)
  {
    using namespace Fiasco;

    Genode::printf("L4_PAGESHIFT=%ld\n",
                   (long)L4_PAGESHIFT);
    return 0;
  }

base-foc/src/test/headers/target.mk:

  TARGET = test-headers
  SRC_CC = test.cc
  LIBS   = env cxx

base-foc/run/headers.run:

  build "core init test/headers"
  create_boot_directory

  install_config {
    <config>
      <parent-provides>
        <service name="ROM"/>
        <service name="LOG"/>
      </parent-provides>
      <default-route>
        <any-service> <parent/> </any-service>
      </default-route>
      <start name="test-headers">
        <resource name="RAM" quantum="1M"/>
      </start>
    </config>
  }

  build_boot_image "core init test-headers"
  append qemu_args "-nographic -m 64"
  run_genode_until "exited with exit value 0" 20

To execute the test, just issue 'make run/headers' from your build
directory.

Cheers
Norman

-- 
Dr.-Ing. Norman Feske
Genode Labs

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