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

[Julian Pidancet]

Fine by me. I will prepare a patch soon.

Thanks.

Julian
On Jan 7, 2012 9:31 PM, "Kevin O'Connor" <kevin at koconnor.net> wrote:

> On Sat, Jan 07, 2012 at 06:27:06PM +0000, Julian Pidancet wrote:
> > On Thu, Jan 5, 2012 at 12:44 AM, Kevin O'Connor <kevin at koconnor.net>
> wrote:
> > >
> > > Is the issue that writes to 0x402 are causing an issue on Xen, or just
> > > that you don't see the debug output?
> > >
> > > What's the origin of 0xe9 - is it a "standard" for debug output?  What
> > > does Xen do today on writes to 0xe9?
> > >
> >
> > Xen has some sort of ring buffer similar to the linux one, that you
> > can access using the xl dmesg command. Every guest access to the 0xe9
> > port is trapped by the hypervisor which appends the characters to the
> > ring buffer. I doubt 0x402 does anything on Xen, aside from beeing
> > trapped in qemu if configured correctly, but I havn't tried.
>
> If you really want this, I'm okay with a patch that introduces
> CONFIG_DEBUG_PORT, and has Kconfig do all the magic of selecting the
> preferred debug port.
>
> That okay?
>
> -Kevin
>
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