[SeaBIOS] [PATCH] qemu: piix: PCI bridge ACPI hotplug support
Gerd Hoffmann
kraxel at redhat.com
Tue Jun 11 09:42:29 CEST 2013
Hi,
>>> Portability:
>>> - Non x86 (or any Linux) platforms don't need any of this code.
>>> They can keep happily using SHPC the way
>>> they always did.
>>
>> Hmm. Is is possible to write a SHPC driver in AML? I think it would be
>> alot better to have one guest/host interface for pci bridge hotplug
>> instead of two.
>>
>> cheers,
>> Gerd
>
> No, it's not possible, SHPC is not designed to be used from ACPI.
>
> Two reasons off the top of my head, there are likely others:
>
> 1. SHPC uses regular PCI interrupts to signal events. It does not signal
> GFE and SCI.
>
> 2. SHPC uses config accesses to get information from device.
> ACPI does not allow config access anywhere except the root bus from ACPI
> (This requirement is designed to give the OS freedom
> to reconfigure PCI in an arbitrary way).
OK, so it's designed for OSes to have native SHPC support. Linux has that?
Quick googling found me Windows Vista+ has it too, correct? So that
leaves Win2k + WinXP versions. Older Windows versions do not support
pci hotplug at all. Win2k is EOL already. WinXP will follow soon.
More users?
/me wonders whenever it is worth hopping through the loops needed to
support ACPI-based hotplug of devices behind bridges in the first place.
cheers,
Gerd
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