[SeaBIOS] seabios fails to send output to the QEMU BIOS debug port

Kevin O'Connor kevin at koconnor.net
Thu Nov 4 14:19:28 CET 2010

On Thu, Nov 04, 2010 at 03:03:10PM +0800, Lin Ming wrote:
> Hi,
> I just find that I can't send output to the QEMU BIOS debug port.
> It's caused by commit d4bded451.
> In qemu-kvm/hw/acpi_piix4.c,
> #define ACPI_DBG_IO_ADDR  0xb044
> Don't know why the DBG was changed from 0xb044 to 0x0402.
> But it still does not work if I changed the port back to 0xb044.
> -        OperationRegion (DBG, SystemIO, 0x0402, 0x01)
> +        OperationRegion (DBG, SystemIO, 0xb044, 0x01)
> Any fix?

That was intentional.  The new system sends output using the regular
bios debug mechanism - you should be able to see that output by adding
the following to qemu command line:

        -chardev stdio,id=seabios \
        -device isa-debugcon,iobase=0x402,chardev=seabios

The above should be simpler then having to recompile qemu with acpi


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