Re: Hypervisor to dom0 communication

[Razvan Cojocaru <rzvncj@gmail.com>]

> I think I'd look at the ioreq stuff in preference to the trace stuff.
> You probably want to use a normal evtchn rather than VIRQ. The code
> which handles HVM_PARAM_BUFIOREQ_PFN and HVM_PARAM_BUFIOREQ_EVTCHN
> should give a reasonable starting point (I think, I'm not actually the
> familiar with this bit of Xen).

Thanks, I'll look that up.

> It might also be useful if you describe your actual end-goal -- i.e.
> what you are ultimately trying to achieve. It may be that there are
> better approaches or even existing solutions or things which are already
> close to your needs.

OK, my immediate end-goal is real-time logging of hypervisor events via 
a dom0 userspace application. These events are always about a currently 
running virtual machine, and said virtual machine is paused at the time.
The userspace tool should be immediately notified, so no polling.

Ideally, in the future, based on information received from the 
hypervisor, the dom0 application would control other virtual machines 
(restart them, shut them down, and so on). This, I'm thinking, could 
either be done by replying to the hypervisor itself via the 
communication channel and do some work there, or, since the application 
is in dom0, do this via libxl or some other available userspace tool. 
However, the paused virtual machine should not be allowed to resume 
unless the userspace application replies that it is OK to resume.

Hope that made sense,
Razvan