Re: [PATCH 1/2] x86, ioapic: Reserve only 128 bytes for IOAPICs

Yinghai Lu
2011-08-26T06:19:07Z

On 08/25/2011 06:41 PM, H. Peter Anvin wrote:
> On 08/25/2011 05:17 PM, Bjorn Helgaas wrote:
>>
>> If the OS allocated the next 128 bytes to another device, it sounds
>> like it would cause a conflict on Intel boxes. This must be an area
>> that differs between vendors. I haven't seen a spec that mentions 256
>> bytes as the required minimum MMIO size for IOAPICs, and apparently
>> the AMD IOAPIC decodes 240 bytes or fewer.
>>
>
> For what it's worth, it's probably a bad idea on x86 for the OS to
> allocate addresses in the 0xFExxxxxx range...
>
for system with more than one ioapic controllers, could have ioapic address rather low.
and those address are allocated to some pci devices BAR by BIOS.

Yinghai