[SeaBIOS] [HELP] The program cause screen mess

eJim Lee lyjforjob at gmail.com
Fri Apr 24 01:49:24 CEST 2015

2015-04-24 5:42 GMT+08:00 Kevin O'Connor <kevin at koconnor.net>:
> On Wed, Apr 22, 2015 at 02:20:51PM +0800, eJim Lee wrote:
>> Hi kevin:
>> If you want to repeat the bug, you can try:
>> 1. Go to "Control panel->Regional and Language
>> Options->Advanced->Language for non-Unicode programs" and select
>> "Chinese (PRC)".
>> 2. reboot
>> 3. run wbc
>> I also tried the program on vmware and looked nice. But something
>> different with qemu about cursor:
>> On qemu with WinXP English: cursor is on screen but not on vmware.
>> Hope these information can help you.
>> Thanks!
>> eJim Lee
>> 2015-04-21 23:41 GMT+08:00 eJim Lee <lyjforjob at gmail.com>:
>> > I have tried it without kvm and bug repeated:
>> > ./build/x86_64-softmmu/qemu-system-x86_64 -chardev stdio,id=seabios
>> > -device isa-debugcon,iobase=0x402,chardev=seabios -m 512 -hda
>> > tmp/xp.append -hdb tmp/data.append
> This issue doesn't seem like a vgabios issue.  It doesn't appear that
> the program calls the vgabios and the program seems to function
> correctly when changing non-vgabios settings.  So, it appears that
> something unknown is the root cause of the intermittent screen
> corruption.

I believe that the program didn't call the vgabios, but I can't
understand why the program work better when I changed vgabios code.
And I believe the issue isn't related to qemu vga device because the
vmware_vgabios also used it and the program worked perfectly.

I found screen mess is related to cursor, because cursor appeared when
the program work on qemu and non-unicode was English but not when on
physical machine.
When I changed the cheight from 16 to 8 in mode 0x12 and deleted the
code calling gfx_write_char, the program is close to work perfact.
So I think the issue may be related to cursor and cheight. I think the
program draw a cursor because XP get something from vgabios and
provide to it.

Kevin, could you tell me something about XP cursor or vgabios
interface leaded to operator drawing cursor or not?

eJim Lee

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