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Date: Tue, 5 Jul 2016 11:23:26 -0400
From: Kevin O'Connor <kevin@koconnor.net>
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Subject: Re: [Qemu-devel] [SeaBIOS] [PATCH 3/3] add serial console support
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To: Gerd Hoffmann <kraxel@redhat.com>
Cc: seabios@seabios.org, qemu-devel@nongnu.org

On Tue, Jul 05, 2016 at 05:07:08PM +0200, Gerd Hoffmann wrote:
> I also hacked up a patch to send output to both vga + serial:
> 
> https://www.kraxel.org/cgit/seabios/commit/?h=serial&id=3afd7b8bb96126b00989f3ae09f451bbec4f00f7
> 
> Not working stable though, seems to corrupt memory, not sure why.
> I'm storing the vgabios int10 vector at 0x5f, then chain-call into
> vgabios via "int 5f" instruction.  Anything obviously wrong with that?

Not sure why it isn't working.  Take a look at
vgaentry.S:entry_timer_hook and vgainit.c:hook_timer_irq() though.
That shows a working example of "hooking" an interrupt.

As an aside, I think it would be better if save/restoring the BDA
cursor position could be avoided.

-Kevin