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Date: Thu, 7 Apr 2011 21:44:17 +0300
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [Qemu-devel] How does the QEMU load the binary files bios.bin
	and vgabios-cirrus.bin?
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Jordan Justen <jljusten@gmail.com>, Bei Guan <gbtju85@gmail.com>, kvm-devel <kvm@vger.kernel.org>, QEMU Developers <qemu-devel@nongnu.org>

On Thu, Apr 07, 2011 at 01:37:14PM -0500, Anthony Liguori wrote:
> >>>>The CS base starts out at 0xf0000 and IP is 0xfff0.  That gives a
> >>>>real address of 0xffff0.  This is usually a trampoline to somewhere
> >>>>else in the space.
> >>>CS descriptor and CS selector don't have to be in sync (big real mode).
> >>Indeed.
> >Another place this will often be seen is SMM, as the SMBASE can easily
> >be>  1MB, but the SMM entry is in 16 bit mode.
> 
> KVM doesn't support SMM although that's not because of this.  KVM
> doesn't allow execution of ROM memory which makes it difficult to
> implement PAM in the way it's intended to be implemented.  This
> makes SMM a bit tricky to make work.  Since there's never really
> been a pressing need to support SMM, to my knowledge, noone has even
> tried.
> 
KVM allows to execute ROM memory (BIOS and option roms run this way). It
just makes it indistinguishable from RAM, but read only memory slot
support shouldn't be too hard. Why ability to execute ROM memory is
needed to support SMM though?

--
			Gleb.