Re: [Xen-devel] Xen attention key

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

> Xen internally registers a series of key handlers. When a key is 
> pressed,
> the corresponding key handler is invoked, which 'printk' (not 'printf' 
> to stdout)
> internal statistical information, very useful for debugging.

I think the 'attention key' is of dubious use, given that domain 0
takes over the VGA console as soon as it starts. Plus the current
'virtualisation' of PS/2 access has never really worked 100% anyway.

For start-of-day (bootstrap) debugging we have the serial line -- I
think that everyone who's doing the type of low-level hacking where
those keys are useful has serial-line acces. 

For later debugging, I think we can just add a temporary DOM0_OP to
execute a keyboard handler, and then use xi_read_console_ring to get
the debug output. The eventual aim should be that most debug keys are
only useful to low-level developers, and any others have some better
defined access method (e.g., we need a better method for pulling
performance counter values out of Xen).

This then allows us to have the keyboard (and mouse) belonging solely
to domain-0 after it has booted, as is already the case for the
display device, which gets rid of the current flawed and pointless
'virtualisation' of PS/2 access.

 -- Keir


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