Re: [PATCH kvm-unit-tests 2/4] Introduce a C++ wrapper for the kvm APIs

Anthony Liguori
2010-11-24T16:56:49Z

On 11/24/2010 10:48 AM, Gleb Natapov wrote:
>> They *aren't* ISA devices. Look at the PIIX3 spec. All of the
>> ports for these devices are positively decoded and not sent over the
>> ISA bus.
>>
>>
> Over the external ISA bus you mean?
>

There is no internal ISA bus. The reality is that the PIIX3 is a
microcontroller and most of the platform devices are probably written in
microcode. That's certainly the case with modern SuperIO chips.

Very specifically, the PIIX3 has a white list of addresses that when it
sees the a PCI bus transaction for those addresses, it asserts DEVSEL#
and then routes the request to the write part of the chip to handle it.
For unhandled transactions, it then forwards them to the ISA bus.

Regards,

Anthony Liguori