On Thu, Mar 9, 2017 at 7:11 PM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> On Thu, Mar 09, 2017 at 03:41:03PM +0000, Gabriele Paoloni wrote:
>> Hi Bjorn and all
>>
>> I have a question regarding bus addresses for IO resources in the
>> ACPI table.
>>
>> The question is if from an ACPI perspective it is legal to have two
>> entries in separate _CRS methods using the same IO bus address.
>>
>> As an example please see the code at the bottom: we have the same
>> bus address starting at 0x0 with (obviously) different offsets
>> leading to different CPU physical addresses. Is this legal?
>
> Yes.
>
> These are on separate PCI buses (PCI0 leads to 0000:00 and PCI1 leads
> to 0001:e0), so there should be no conflict. Those are completely
> independent PCI buses, and their bus address spaces are also
> independent.
>
> You do have to make sure the CPU physical addresses don't conflict, of
> course.
Ok. My reading of the ia64 code was that it would reject this as being
overlapping resources, but I was probably misreading then.
What is the expected way to deal with a device using an I/O resource
that is not a child of either PCI host bridge in this case (e.g. a
BMC behind a PCI-LPC bridge)? Is this only allowed to exist below
the device that provides the respective I/O space?
Arnd
