Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios

[Kevin O'Connor]

On Sun, Nov 22, 2009 at 05:38:09PM +0200, Gleb Natapov wrote:
> On Sun, Nov 22, 2009 at 04:31:24PM +0100, Sebastian Herbszt wrote:
> >    // Write protect bios memory.
> >    make_bios_readonly();
> Hmmm. How is tpr patching works then? It relies on ability of a guest to
> write into BIOS memory region. Need to retest if it actually works I
> guess.

The last time I looked, the TPR patching backend forced the "vapic"
pages to be writable (effectively overriding the bios decision to make
it readonly).

> > Bad things could happen if someone modifies the BIOS because it's 
> > unprotected
> > (e.g. VM crash).

I'm not sure why modification of the BIOS would cause a VM crash.  If
this is true, then a malicious guest could unlock the ram and write to
it for the same effect.

-Kevin