Re: The way of mapping BIOS into the guest's address space

[Cyrill Gorcunov <gorcunov@openvz.org>]

On Tue, Feb 14, 2012 at 01:10:59PM +0200, Pekka Enberg wrote:
> On Tue, Feb 14, 2012 at 1:03 PM, Yang Bai <hamo.by@gmail.com> wrote:
> > Since on X86, bios is always at the end of the address space, so I
> > have some thought about how to implement the seabios support for kvm
> > tool.
> >
> > 1. using kvm__register_mem to map the end of address space to the
> > guest then copy the code of seabios to this mem region. Just emulating
> > the bios chip.

I think this is what should be done.

> >
> > 2. leave the bios code alone and don't touch the guest's address
> > space. If the guest accesses the address belonging to the bios, it
> > will be an IO request and we can emulate the IO access to the bios
> > chip.
> >
> > Any ideas about this?
> 
> The latter solution doesn't make any sense to me. Cyrill, do we really
> need to put the BIOS at the end of the address space? Don't we have
> unused space below 1 MB?

I don't remember for sure how SeaBIOS works actually. What I rememer
is that it aquires all hw environment might have. So without real look
into seabios code I fear I can't answer. But reserving end of 4G address
space for bios copy sounds reasonable if we going to behave as real
hardware. Maybe we could poke someone from KVM camp for a hint?

	Cyrill