Re: [BUG} libxl.c:5947:libxl_send_trigger: Send trigger 'reset' failed: Function not implemented

[Ian Campbell <ian.campbell@citrix.com>]

On Wed, 2016-02-10 at 11:51 +1100, Alex Braunegg wrote:
> Many thanks for the detailed information and analysis - so potentially
> chasing something that cannot occur to a guest if the Windows PV Drivers
> are not installed.
> 
> > You might want to change this now. ;-)
> 
> No issue there - the guest was destroyed after grabbing the debug
> details. The full .cfg might be useful for someone else down the track.
> 
> > I'd strongly recommend installing some PV drivers into the guest, 
> 
> So this leads to another question. Is there a mechanism that exists today
> that allows via xl or some other Xen tool to 'probe' the guest as to if
> the PV drivers are loaded?

There is a function internal to libxl (libxl__domain_pvcontrol) which
answers this question (by looking at the callback IRQ).

I suppose it would be reasonable to expose that formally in the libxl
public API in some form, although it is also the case that any function
which uses PV control mechanisms performs (or at least should perform) this
check and return ERROR_NOPARAVIRT if pv control is not avaiable, so
application code can try PV and fallback to other methods (as xl does).

[...]
> Including ' xenctrl.h' in xl_cmdimpl.c would also be needed so that the
> function 'xc_hvm_param_get' could be used.

libxc (xenctrl.h) is not a stable interface and it is a design goal of
libxl that toolstacks should only need to use libxl interfaces for their
toolstack oriented operations. So this functionality would need to be
reflected in the stable libxl API for use by xl (and libvirt, and other
toolstacks people might write)

Ian.