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Re: [Qemu-devel] Regression: more 0.12 regression (SeaBIOS related?)

From: Roy Tam
Subject: Re: [Qemu-devel] Regression: more 0.12 regression (SeaBIOS related?)
Date: Wed, 10 Mar 2010 13:24:27 +0800

2010/3/10 Kevin O'Connor <address@hidden>:
> On Wed, Mar 10, 2010 at 11:49:48AM +0800, Roy Tam wrote:
>> 2010/3/10 Kevin O'Connor <address@hidden>:
>> > SeaBIOS has a wealth of debugging information that could help solve
>> > these issues.
>> Tried this this BIOS and 2 debug logs generated.
>> seabios-debug.log is booting fdos0138.img and closes QEMU after boots to 
>> prompt.
>> seabios-debug-2.log is booting fdos0138.img and type something and
>> Illegal Instruction occurred.
> I don't see an "Illegal Instruction" message.  Instead, I see the
> keyboard just not working.  What qemu version and what command line
> did you use?

latest git today. when you type fast.

> I've tracked down why keys are lost on SeaBIOS and not lost on Bochs
> BIOS.  The fdos0138.img code is taking over the irq handler for the
> ps2 port hardware irq.  When the irq fires, it reads the ps2 port for
> the key data and then calls the bios irq handler assuming it will
> reread the key and process it.  However, SeaBIOS reads the ps2 port
> status indicator and finds that there is no data pending (because the
> key was already read by the fdos0138.img irq handler).
> Bochs BIOS just reads the data from the ps2 port and assumes it is for
> the keyboard.  SeaBIOS verifies the data being read and wont process
> random data from the port.
> What the fdos0138.img image is doing is broken - once it reads the key
> from the ps2 port, nothing stops a new key from being read the next
> time something reads from the port.  Indeed, although the keyboard
> works in qemu-0.11 for fdos0138.img, if one types fast they'll see
> duplicate and lost keys.

But it is how programs(Chinese/Japanese/Korean Display Systems,
GW-BASIC, etc.) in the past get input from keyboard.
"Consider" legacy as "broken" is wrong IMHO.

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