[SeaBIOS] [edk2] [PATCH 0/8] OvmfPkg: reset-related changes

[Laszlo Ersek]

On 02/22/13 15:55, David Woodhouse wrote:
> On Fri, 2013-02-22 at 04:23 +0100, Laszlo Ersek wrote:
>> Patches 1 to 6 upgrade the FADT to ACPI 2.0 and present the PIIX3
>> Reset Control Register in it.
> 
> Hm. I can still trigger the soft reset loop in SeaBIOS, but perhaps not
> in a circumstance that we care about...
> 
> I've fixed Qemu to do the proper hard reset on 0xcf9 but not any other
> reset method. I'm running with KVM on an old machine without
> "unrestricted guest" support.
> 
> I've fixed SeaBIOS to look for the ACPI RESET_REG and use it, and that
> part *works*... but SeaBIOS only *sees* the ACPI table when we boot a
> legacy OS. If I boot an EFI OS and then do a soft reset via the keyboard
> controller ('echo -en \\xfe | dd of=/dev/port bs=1 seek=$((0x64))'),
> SeaBIOS hasn't seen the ACPI tables, still uses the keyboard controller
> as its first choice of reset method, and still does its reset loop as
> before.
> 
> Do we actually *care* about that? Do we expect any EFI OS to be doing a
> keyboard reset instead of using ACPI or the runtime services Reset call?

http://thread.gmane.org/gmane.comp.emulators.qemu/195351/focus=2169

If you evaluate the pseudo-code there with the input you described
above, I think we can conclude this is the KVM problem again, and that
we shouldn't care. When you actually *want* soft reset, there's nothing
qemu can do to cover up the problematic jump target that comes from the
first part of the pseudo-code.

Laszlo