[SeaBIOS] [HELP] The program cause screen mess

eJim Lee lyjforjob at gmail.com
Mon Apr 20 19:57:53 CEST 2015

2015-04-21 0:45 GMT+08:00 Kevin O'Connor <kevin at koconnor.net>:
> On Tue, Apr 21, 2015 at 12:23:15AM +0800, eJim Lee wrote:
>> Yes, I have tried gtk_monitor+VGA+seaVGABIOS.
> Did you see screen corruption when you tried gtk_monitor+VGA+seaVGABIOS?

I have repeated screen mess at every time.

>> The following is my log:
>> =====================================================
>> LYJ-UPC:~/qemu$ ./build/x86_64-softmmu/qemu-system-x86_64 -enable-kvm
>> -hda tmp/xp_rcc.append -hdb tmp/data.append -m 1024 -smp 1 -device
>> VGA,romfile=/home/lyj/qemu/seabios/out/vgabios.bin -net none -chardev
>> stdio,id=debugcon -device isa-debugcon,chardev=debugcon,iobase=0x0402
>> SeaBIOS (version rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org)
> [...]
>> set VGA mode 143
>> VBE current mode=4143
>> VBE mode info request: 4143
>>                                                        <---- start wbc
>> set VGA mode 3
>> set VGA mode 3
>>                                                        <---- exit wbc
>> VBE mode set: 4143
>> set VGA mode 143
>> VBE current mode=4143
>> VBE mode info request: 4143
>> qemu: terminating on signal 2
> Was there screen corruption during the above log?

There is nothing to be outputted. After outputting "set VGA mode 3"
twice, I couldn't get anything.
I guessed the program do all and not invoked vgabios interface.

>> I debugged both vgabios and qemu, and found the wbc didn't use vgabios
>> interface but changing vgabios caused that the wbc run better.
>> I found the wbc r/w vga register directly to set vga mode when added
>> printf on vga_update_display in qemu.
>> Uncomfortably, gfx_write_char have never been invoked and I deleted it
>> in vgafb_write_char, that bring screen looking better. What happend? I
>> can't understand.
> I would guess the defect has some randomness to it and minor changes
> to code layout can cause or avoid the problem.

I agree.

>> Kevin, did you repeat screen mess?
> I've tried several different configurations (including the last
> command line you sent), but I have not been able to reproduce any
> screen corruption.

I have repeated it at every time on server, my laptop or my pc.
I tried it on ubuntu 14.04, centos 6.5, kernel 3.10.67 and kernel. etc.
What is the difference? I used guest os is xp sp3. What yours?
I will try again with environment same as yours.

> -Kevin

eJim Lee

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