[SeaBIOS] [PATCH] Use dedicated HVM debug io port for Xen

Julian Pidancet julian.pidancet at gmail.com
Thu Jan 5 01:26:31 CET 2012


On Thu, Jan 5, 2012 at 12:05 AM, Kevin O'Connor <kevin at koconnor.net> wrote:
> On Wed, Jan 04, 2012 at 05:19:59PM +0000, Julian Pidancet wrote:
>> On Sat, Nov 5, 2011 at 2:43 AM, Julian Pidancet
>> <julian.pidancet at gmail.com> wrote:
>> > When running on Xen, use Xen debug io port as debug output instead
>> > of Bochs one.
>
> I'm leery of having multiple "magic" debug ports.  Is it possible for
> Xen to pick up port 0x0402 (or use the qemu style -device
> isa-debugcon,iobase=0x402 command line option)?
>

Well, I initially thought that 0x402 was a bochs specific debug port.
Now I'm not too sure about this any longuer, because I just found in
the bochs documentation that 0xe9 can be used as well:
http://bochs.sourceforge.net/doc/docbook/user/bochsrc.html
(port_e9_hack)

Can you enlighten me as to the origin of the 0x402 port ?

I really doubt picking up a new debug port in xen would be acceptable
because 0xe9 has been around for a long time and it would certainly
break legacy code.

-- 
Julian



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