[coreboot] SeaBIOS, serial output, and grub

Ward Vandewege ward at gnu.org
Fri May 1 23:45:51 CEST 2009

On Thu, Apr 30, 2009 at 10:39:31PM -0400, Kevin O'Connor wrote:
> On Thu, Apr 30, 2009 at 10:26:56PM -0400, Kevin O'Connor wrote:
> > What's really odd, is that if I have sgabios on, then grub does work
> > okay.  I didn't catch this last night because I was also playing with
> > sgabios at the same time.  As a guess, sgabios is reinitializing the
> > serial port back to a way grub is okay with.  This may be specific to
> > qemu, but it's something to look into.
> Oops - if qemu/coreboot/seabios/sgabios/grub, then sgabios forwards
> the grub screen over serial - grub itself still wont talk to the
> serial directly.  (If I run qemu/seabios/sgabios/grub then I get two
> copies of the grub messages - one from grub serial and one from grub
> screen via sgabios.)

Hmm. I'm not seeing that on h8dme. This is my cbfs:

./cbfstool ./coreboot.rom print
coreboot.rom: 1024 kB, bootblocksize 266240, romsize 1048576, offset 0x0
Alignment: 16 bytes

Name                           Offset     Type         Size
normal/payload                 0x0        payload      65635
fallback/payload               0x10090    payload      65635
pci1002,515e.rom               0x20130    0x00000000   45056
genroms/sgabios.rom            0x2b170    0x00000000   3169
pci10de,0373.rom               0x2be10    0x00000000   57344

I've got a vga rom and gpxe in there, in addition to sgabios.

Here's a boot log (seabios head, coreboot r4232 + Myles' serial patch from


And here's one without gpxe in the cbfs:


Basically, grub's super slow, trying to write to serial, but as you can see
no grub output ever appears there. Sometimes grub actually displays its menu
on the vga console after the 'press any key to continue' lines (if I bang
enough keys, it seems), but most of the time it just does the default, which
is (nonfunctioning) serial.


Ward Vandewege <ward at fsf.org>
Free Software Foundation - Senior Systems Administrator

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