[vbox-dev] IMachine methods in source code?

Johannes DeWitt johannesynt at gmail.com
Wed Jun 11 12:38:39 UTC 2014

Thanks you for your perfect explanation.
I wanted to use stdio.h because i was looking for a way to read some values
from outside, while a virtual machine is in runtime; so my idea was to use
the fopen function to read values from a normal file (txt or something).
But now i understand why i can't use stdio.h (kernel mode etc).

So, in VMMAll/ is it IMPOSSIBILE to read a value from another file? I read
your answer, i understand that a possibile way is from tm struct, but if i
need to use a value that can change in rumtime? My achievement is to read
(in VMMAll/ ) value from an external file, and read this value more times,
and this value can change during the execution.

For example, i need to execute a part code ONLY when i want, so my idea was
to write ( in a VMMALL/ .cpp file) code like this:

x= get value from external file MYVALUE (xml or somehting) (in this file,
the value is 0)
if (x) { do something;}

every time virtualbox execute this code, nothing happend.

after a while, from extern i change the value in the file MYVALUE (from 0
to 1)
Now, when virtualbox execute the code above, it enters in the {do

I hope you can understand my example.

2014-06-11 13:51 GMT+02:00 Klaus Espenlaub <klaus.espenlaub at oracle.com>:

> On 09.06.2014 12:51, Johannes DeWitt wrote:
> > I tried to use this function in VMM/VMMAll/TMAll.cpp, but when i
> > compile, i receive this: ‘CFGMR3GetRoot’ was not declared in this scope
> > I added #include <VBox/vmm/cfgm.h, but atill have this error.
> TMAll.cpp is code which is compiled several times, once for the
> userland, once for kernel mode etc etc., which shares data. In this code
> it's impossible to deal with CFGM settings. Everything must be already
> stored in the VM or VMCPU structure or somewhere reachable from there
> while in userland. See VMMR3/TM.cpp how the TM settings are handled (it
> already uses CFGM), your needs probably can be covered by adding a few
> such settings.
> Note that all extradata keys (see documentation of VBoxManage extradata)
> starting with VBoxInternal/ are stored in CFGM automatically, i.e. you
> need to set VBoxInternal/TM/foo to some value in order to have it
> available in VMMR3/TM.cpp.
> > Any ideas? I tried also to include <stdio.h> for others achievements,
> > but i recieve an error too (however in others .cpp files i can use
> > stdio.h without any problems): i don't understand why
> See above. One can't use the normal stdio.h functionality from kernel. A
> subset of the Runtime functionality is available, and I don't think you
> need anything which isn't already used by VMMAll/*.cpp.
> Klaus
> > 2014-06-06 14:51 GMT+02:00 Frank Mehnert <frank.mehnert at oracle.com
> > <mailto:frank.mehnert at oracle.com>>:
> >
> >     Johannes,
> >
> >     On Friday 06 June 2014 14:46:46 Johannes DeWitt wrote:
> >      > I, i need to use come IMachine methods in source code. For
> >     example, if a
> >      > want to use the GetSettingsFilePath() function (used in
> >      > tstVBoxAPIXPCOM.cpp) in a cpp file of the source code, for
> >     example in a cpp
> >      > file in /src/VBox/VMM/VMMAll/, how can i do it?
> >      > And which headers files i need to include?
> >
> >     that's actually not the intended way to use !VirtualBox. VMM and Main
> >     are strictly separated, and in particular the IMachine code you are
> >     talking about lives in VBoxSVC while the VMM code lives in the
> >     client (either the VirtualBox process or the VBoxHeadless process).
> >
> >     Inside VMM you should always have a pRoot handle,
> >
> >        pRoot = CFGMR3GetRoot(pVM);
> >
> >     Using this pRoot handle you can access the CFGM tree for that
> particular
> >     VM.
> >
> >     Kind regards,
> >
> >     Frank
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