Re: Ideas for PV on SeaBIOS

[Paolo Bonzini <pbonzini@redhat.com>]

On 05/19/2011 10:01 AM, Ian Campbell wrote:
> We had a bit of a brainstorm yesterday and someone suggested that
> perhaps qemu could deal with it when it sees the I/O ports for the
> emulated device unplug get hit.

You could imagine doing the unplug even under an OS that uses INT 13h. 
PV drivers also aren't forced to do the unplug: RHEL5 guests (up to 5.7 
at least) use blacklisting, and the Red Hat PV drivers for Windows use a 
filter driver because I never got the unplug to work.

If SeaBIOS is guaranteed to never reinitialize the callback via, 
trapping writes to HVM_PARAM_CALLBACK_IRQ with an SMI-like effect sounds 
like the way to go, as everybody probably agrees at this point.  You 
could also initate the shutdown from dom0, which you could easily do via 
ACPI even. ;)

STORE_PFN and STORE_EVTCHN parameters are usually written only by dom0 
(in fact perhaps setting them could be made a privileged operation), 
which makes them less ideal.

Paolo