Re: [Qemu-devel] possible regression in qemu-kvm 0.13.0 (memtest)

[Stefan Hajnoczi]

On Sat, Dec 25, 2010 at 7:02 PM, Peter Lieven <address@hidden> wrote:
> this was the outcome of my bisect session:
>
> 956a3e6bb7386de48b642d4fee11f7f86a2fcf9a is first bad commit
> commit 956a3e6bb7386de48b642d4fee11f7f86a2fcf9a
> Author: Blue Swirl <address@hidden>
> Date:   Sat May 22 07:59:01 2010 +0000
>
>    Compile pckbd only once
>
>    Use a qemu_irq to indicate A20 line changes. Move I/O port 92
>    to pckbd.c.
>
>    Signed-off-by: Blue Swirl <address@hidden>
>
> :100644 100644 acbaf227455f931f3ef6dbe0bb4494c6b41f2cd9 
> 1a33d4eb4a5624c55896871b5f4ecde78a49ff28 M      Makefile.objs
> :100644 100644 a22484e1e98355a35deeb5038a45fb8fe8685a91 
> ba5147fbc48e4faef072a5be6b0d69d3201c1e18 M      Makefile.target
> :040000 040000 dd03f81a42b5162c93c40c517f45eb9f7bece93c 
> 309f472328632319a15128a59715aa63daf4d92c M      default-configs
> :040000 040000 83201c4fcde2f592a771479246e0a33a8906515b 
> b1192bce85f2a7129fb19cf2fe7462ef168165cb M      hw
> bisect run success

Nice job bisecting this!  I can reproduce the Memtest86+ V4.10 system
reset with qemu-kvm.git and qemu.git.

The following code path is hit when val=0x2:
if (!(val & 1)) {
    qemu_system_reset_request();
}

I think unifying ioport 0x92 and KBD_CCMD_WRITE_OUTPORT was incorrect.
 ioport 0x92 is the System Control Port A and resets the system if bit
0 is 1.  The keyboard outport seems to reset if bit 0 is 0.

Here are the links I've found describing the i8042 keyboard controller
and System Control Port A:
http://www.computer-engineering.org/ps2keyboard/
http://www.win.tue.nl/~aeb/linux/kbd/A20.html

Blue Swirl: Any thoughts on this?

Stefan