Re: [Xen-devel] Design doc of adding ACPI support for arm64 on Xen

[Shannon Zhao <zhaoshenglong@xxxxxxxxxx>]

On 2015/8/12 4:43, Konrad Rzeszutek Wilk wrote:
> On Wed, Aug 05, 2015 at 09:03:06PM +0800, Shannon Zhao wrote:
>>
>>
>> On 2015/8/5 20:48, Julien Grall wrote:
>>> On 05/08/15 12:49, Shannon Zhao wrote:
>>>>>>> That's great!
>>>>>>> Keep in mind that many ARM platforms have non-PCI busses, so I think
>>>>>>> we'll need an amba and a platform bus_notifier too, in addition to the
>>>>>>> existing pci bus notifier.
>>>>>>>
>>>>>
>>>>> Thanks for your reminding. I thought about amba. Since ACPI of current
>>>>> linux kernel doesn't support probe amba bus devices, so this
>>>>> bus_notifier will not be used at the moment. But there are some voice
>>>>> that we need to make ACPI support amba on the linux arm kernel mail
>>>>> list. And to me it doesn't matter to add the amba bus_notifier.
>>> This comment raised one question. What happen if the hardware has MMIO
>>> region not described in the ACPI?
>>>
>> This sounds weird. If a device is described in ACPI table, it will not
>> describe the MMIO region which the driver will use? Does this situation
>> exist?
>>
>> If the hardware has mmio region not described in the ACPI, how does the
>> driver know the region and use it?
> 
> On the x86 world we would query the PCI configuration registers and read
> the device BAR registers. Those would contain the MMIO regions the
> device uses.
> 
> But x86 is funny and you do say 'many .. ARM .. have non-PCI buses' - which
> would imply you have not hit this yet.
> 
> Are PCI devices interrogated differently on ARM? No configuration registers?
>>

For PCI devices, on ARM it will reuse the existing bus_notifier
"xen_pci_notifier" to call hypercall to map mmio regions. And other
operates are same with X86.

Thanks,

-- 
Shannon


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