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

From: Kevin O'Connor
Subject: Re: [Qemu-devel] Re: POST failure (loop) with isapc and seabios
Date: Sun, 22 Nov 2009 12:40:24 -0500
User-agent: Mutt/1.5.19 (2009-01-05)

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.


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