Re: [Qemu-devel] [edk2] OvmfPkg reset [was: Distinguish between reset types]

[Paolo Bonzini]

Il 21/02/2013 19:24, Laszlo Ersek ha scritto:
>> > (1) The reset capability that OVMF exports via ACPI -- I agree that I
>> > should be effecting the 0xCF9 thing in the appropriate table.
> On a second thought, this will require a new build -D flag, or a PCD.
> 
> I'm not worried about the ACPI 1.0 --> ACPI 2.0 change in the FADT, the
> table struct itself forward compatible.
> 
> However currently we're not saying anything about the reset capabilities
> of the platform. A client looking at the FADT for reset info will find
> nothing and follow its own logic, which may or may not include writing
> to 0xCF9, but we don't have any part in it.
> 
> If now the FADT starts to claim 0xCF9 on a qemu version that doesn't
> actually support it, we could mislead the client. Unless we can
> interrogate qemu about the support (and I think we can't), we'll have to
> depend on a build-time option. (Or should I shoehorn it into -D CSM_ENABLE?)
> 
> Jordan, what do you think?

ACPI tables are hosed enough on some real system that we can assume that
all guests will fall back to something else---typically a keyboard
controller reset.

See the sequence that Windows does: ACPI, kbd, ACPI, kbd.

Paolo