Re: [SerialICE] r87 - trunk/qemu-0.11.0

[Stefan Reinauer]

[e-mail] wrote:
> What does Qemu do when 0xcf9 is sent to bios Stefan?

Hi Joe,

The I/O 0xcf9 is the "reset register" on most x86 systems. Writing
certain values to it will cause a hard or soft reset.
Qemu however does not emulate this behavior - as far as I can tell - it
certainly does not while SerialICE is active, because all IO accesses go
to the target (or are caught by LUA)

Basically what's missing in the LUA script to make resets via cf9 work
properly is adding the following to SerialICE_IO_write_filter:

if port == 0xcf9 and data == 0x06 then
        SerialICE_system_reset()
        return false, data
   end

The serial communication code has been rewritten for the last release to
be quite hick-up safe.. This means Qemu does not get out of sync if the
target reboots, so all that needs to happen after a reboot of the target
is to reboot the VM on the host, too, to let it start at the reset
vector again... Otherwise it'll just try to execute code right after the
out to cf9.. which is usually an endless loop as a safe guard.

Stefan

r87 - trunk/qemu-0.11.0

[Stefan Reinauer]

Stefan Reinauer wrote:
> Basically what's missing in the LUA script to make resets via cf9 work
> properly is adding the following to SerialICE_IO_write_filter:
>
> if port == 0xcf9 and data == 0x06 then
>         SerialICE_system_reset()
>         return false, data
>    end

I will add this in one of the next commits. But I think it's time to
start using the device tree code in LUA, or else it'll become too
crowded with corner cases of my test machine, which currently has five
or six "automatic loop skips":

if ( port == 0x60 and data == 0xaa ) then
        if ( regs.eip == 0xbd6d and regs.eax == 0x8aa and regs.ecx ==
0x00fffff0 ) then
            -- Loop does IO at f000:bd6d. Execute the first 16 IO accesses
            printf("Skipping keyboard timeout...\n")
            regs.eax = 0x01aa -- ah is the outer loop counter
            regs.ecx = 0x0010 -- and the last 16
        end
    end

Stefan

r87 - trunk/qemu-0.11.0

On December 5, 2009 at 11:31 PM Stefan Reinauer  wrote:
> [e-mail] wrote:
> > What does Qemu do when 0xcf9 is sent to bios Stefan?
>
> Hi Joe,
>
> The I/O 0xcf9 is the "reset register" on most x86 systems. Writing
> certain values to it will cause a hard or soft reset.
> Qemu however does not emulate this behavior - as far as I can tell - it
> certainly does not while SerialICE is active, because all IO accesses go
> to the target (or are caught by LUA)
>
> Basically what's missing in the LUA script to make resets via cf9 work
> properly is adding the following to SerialICE_IO_write_filter:
>
> if port == 0xcf9 and data == 0x06 then
>          SerialICE_system_reset()
>          return false, data
>     end
>
> The serial communication code has been rewritten for the last release to
> be quite hick-up safe.. This means Qemu does not get out of sync if the
> target reboots, so all that needs to happen after a reboot of the target
> is to reboot the VM on the host, too, to let it start at the reset
> vector again... Otherwise it'll just try to execute code right after the
> out to cf9.. which is usually an endless loop as a safe guard.

Yeh I know what 0xcf9 is, I just was not sure what Qemu did with it.
Sweet! Great work Stefan! I will have to get my head out of my ass and try it
out :-)

Thanks,
Joseph Smith
Set-Top-Linux
www.settoplinux.org