[coreboot] Fwd: SimNOW VGA int 1a

[ron minnich]

On Thu, Oct 16, 2008 at 3:28 PM, Carl-Daniel Hailfinger
<c-d.hailfinger.devel.2006 at gmx.net> wrote:

> Think of point 1-4 as one "atomic" operation. pci_conf1_read_config32
> does not call any other function, so simply unshare that and be happy.
>

it's worse than that. We found when doing this years ago that some
nvidia vga bios'en don't call pcibios. They just set config space. But
they might
do INT10 for other reasons. The general case is that a vga bios might
do something in config space that maps out ROM, since they "know" that
there is no
issue, and then do an INT 10, and if that happens, no code can be in
rom -- including printk.

After the things I've seen, up to and including self-modifying code,
I am not willing to trust a VGA bios not to do something really
foolish.

So here's another option. We've always run out of high memory. But v3
has this nice 32-bit address space, and the ability to call rom, but
most of it runs out of ram now. coreboot ROM segment is now 20K or
less.

Why not just run the ROM section of coreboot in the F segment? What
would that harm?

If we do this, the problem goes away.



> I'm not completely getting this. Do we run the binary blob from inside
> coreboot or does SeaBIOS perform that task?

coreboot. vm86.

> If coreboot does it, we have some trapping code for BIOS emulation anyway.

which is where the problem is.

ron