On 03/21/2013 08:58 AM, Michael S. Tsirkin wrote:
>>
>> Most of them do really ugly hacks in hardware (like putting in a "back
>> door" in config space) to make that possible.
>
> config space register that let us access
> registers within BAR actually sounds pretty reasonable.
> Way better than an I/O BAR.
>
It is really, really, nasty, not to mention slow.
>>>
>>> Problem is, BIOS and OS normally assume failure to allocate
>>> any resources means card won't function and disable it.
>>> So it does not seem to be worth it to have such a
>>> device specific failover ability.
>>>
>>
>> That is a violation of the PCIe spec; the PCIe spec specifically states
>> that failure to allocate an I/O BAR should still allow the device to
>> function.
>
> Where does it say this?
In PCI Express 1.1 base, it is section 1.3.2.2, third bullet.
-hpa
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