Re: [Qemu-devel] [SeaBIOS] KVM call agenda for 2013-05-28

[Gerd Hoffmann <kraxel@redhat.com>]

  Hi,

>>> possible complexity of having to regenerate
>>> tables on a vm reboot,
>>
>> Why tables should be regenerated at reboot?  I remember hotplug being
>> mentioned in the call.  Hmm?  Which hotplugged component needs acpi
>> table updates to work properly?  And what is the point of hotplugging if
>> you must reboot the guest anyway to get the acpi updates needed?
>> Details please.
> 
> I think it's a mistake. I sent a mail explaining this part.

Saw it meanwhile.

>> Also mentioned in the call: "architectural reasons", which I understand
>> as "real hardware works that way".  Correct.
> 
> Not exactly. Real hardware is very likely to have
> most of the tables pre-generated in ROM, load
> them and tweak them in the minor way.

>From a quick look it seems coreboot has a static (iasl-compiled) dsdt
and generates everything else.

http://review.coreboot.org/gitweb?p=coreboot.git;a=blob;f=src/mainboard/emulation/qemu-x86/acpi_tables.c

>> Agree on this one.  Ideally the acpi table generation code should be
>> able to gather all information it needs from the qom tree, so it can be
>> a standalone C file instead of being scattered over all qemu.
> 
> Did you look at the patchset I posted?

Very briefly only.

> Generation is in a standalone C file there.

Good.

> However, if you mean we should do things like
> 
> if (Device_id == foobar) {
> }
> in once central place, I disagree.
> I think that's nasty, adding devices would
> mean touching this central registry.

No, I mean more "lookup PIIX4_PM object + check disable_s3 property"
instead of having code for it in hw/acpi/piix4.c or using global variables.

cheers,
  Gerd