Re: X server in dom0: Bad VBT signature

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Sun, Sep 02, 2012 at 04:42:17PM -0400, Mouse wrote:
> > it's the memory-mapped address space which is causing problem for
> > Xen, because the physical addresses are not real machine addresses,
> > they are translated by the hypervisor, and may have the same address
> > as real machine address but point to something different.
> 
> Sounds as though Xen is the problem, in that it is putting two
> different things (RAM and memory-mapped hardware) at the same
> (emulated-)physical address.  Or am I still misunderstanding?

No, Xen does in fact add an address space: emulated-physical address,
which is for RAM. memory-mapped hardware remains in the machine address
space. These are 2 distinct addresses spaces, while on plain x86 it's
the same space. In kernel, we properly make the disctinction.
The problem is /dev/mem, or it's usage by X which assumes it can access
memory-mapped hardware from here.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--