Re: [Qemu-devel] Where is vga-rom mapped in guest system memory?

[Jaeyong Yoo]

> I rely on the qemu debug port rather than on serial:
> 
>   -debugcon file:debug.log -global isa-debugcon.iobase=0x402
> 
> Check the DEBUG_IO and DEBUG_LEVEL settings in the SeaBIOS config as well.

Thanks Laszlo! Now I can see the log message in VirtualBox vgabios with qemu
debug port.

By the way, I've got one more question, which is very strange for me.

I tried to print a string and the values read by the string address do not look
correct. More specifically, I wrote the following code in VirtualBox vga-bios:

char *msg = "Start Vgabios\n";

for (i = msg; ++i; *i != 0)
{
    outb(0x402, *i);
}

And, I expect to see the message "Start Vgabios" in the debug port, but it 
doesn't
work. If I object-dump the related parts in VirtualBox vga-bios, I can see that 
the
msg (msg = 0x7eea) properly contains "Start Vgabios". And, if I print the value 
of i
in vga-bios, it gives 0x7eea (which is correct address). Then I expect that *i 
should
be 'S' but *I gives zero. I checked the vga-rom size field and it properly 
covers the
actual size of vgarom. Then, I think qemu properly map the entire vgarom in the 
proper,
so it won't be an issue.

Is there some issues with memory addressing that I'm missing?


Best regards,
Jaeyong