Here is some more info on the double character printing problem in #740464
1) seabios default
In the Debian seabios source (version 1.7.4-4), if you look at line 437 of
src/optionroms.c
ScreenAndDebug = romfile_loadint("etc/screen-and-debug", 1);
it's defaulting to having the debug printing enabled.
Upstream of the same file (but line 435) is the same,
http://review.coreboot.org/gitweb?p=seabios.git;a=blob;f=src/optionroms.c;h=
93d9d2fe6507482b3ba0b6782a13887fb8a0fdf7;hb=HEAD#l435
2) Fedora
I heard a report that using sgabios on Fedora/RHEL does not have this
double priinting problem. I wasn't able to easily determine if they have
patches to change this behavior
The Fedora qemu source doesn't appear change anything related
http://pkgs.fedoraproject.org/cgit/qemu.git
The Fedora seabios doesn't appear to change anything related
http://pkgs.fedoraproject.org/cgit/seabios.git
It's possible they are doing something like setting a debug level
differently that results in differences, or I missed something, or they are
changing it elsewhere. First step would be testing to confirm they don't
have the problem.
3) I don't know if this is relevant, but in the upstream sgabios design
document, line 240
http://code.google.com/p/sgabios/source/browse/trunk/design.txt#240
it says
"When lilo 22.6 is detected, SGABIOS now knows how to disable
lilo's serial output in favor of its own. This avoids having
double character output from both serial and VGABIOS interleaved."
I am seeing the problem with pxelinux 4.06.
4) Potential solutions
I don't know what the purpose of screen-and-debug is, it might be that
it could be disabled with no ill effects. So here are some potential
solutions
* Change seabios screen-and-debug default to 0 in the seabios package
* Have the seabios package produce an alternate bios.rom with
screen-and-debug disabled, then kvm could use it with "-bios"
* Add a -boot suboption for screen-and-debug to kvm and have it default
to enabled
* Add a -boot suboption for screen-and-debug to kvm and have it default
to disabled
* Add hacks to sgabios to have it detect and work around bootloaders
that have the problem.
* Come up with a more generic sgabios fix.
* Something else
Feel free to reassign this bug to seabios, sgabios, etc or forward
elsewhere depending on what makes sense.
Thanks,
--
Matt Taggart
[email protected]
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