Re: [Xen-devel] Design doc of adding ACPI support for arm64 on Xen - version 2

[Shannon Zhao <zhaoshenglong@xxxxxxxxxx>]

On 2015/8/11 17:46, Julien Grall wrote:
> On 11/08/15 03:09, Shannon Zhao wrote:
>> Hi Julien,
> 
> Hi Shannon,
> 
>> On 2015/8/7 18:33, Julien Grall wrote:
>>> Hi Shannon,
>>>
>>> Just some clarification questions.
>>>
>>> On 07/08/15 03:11, Shannon Zhao wrote:
>>>> 3. Dom0 gets grant table and event channel irq information
>>>> -----------------------------------------------------------
>>>> As said above, we assign the hypervisor_id be "XenVMM" to tell Dom0 that
>>>> it runs on Xen hypervisor.
>>>>
>>>> For grant table, add two new HVM_PARAMs: HVM_PARAM_GNTTAB_START_ADDRESS
>>>> and HVM_PARAM_GNTTAB_SIZE.
>>>>
>>>> For event channel irq, reuse HVM_PARAM_CALLBACK_IRQ and add a new
>>>> delivery type:
>>>> val[63:56] == 3: val[15:8] is flag: val[7:0] is a PPI (ARM and ARM64
>>>> only)
>>>
>>> Can you describe the content of flag?
>>>
>>
>> This needs definition as well. I think it could use the definition of
>> xenv table. Bit 0 stands interrupt mode and bit 1 stands interrupt
>> polarity. And explain it in the comment of HVM_PARAM_CALLBACK_IRQ.
> 
> That would be fine for me.
> 
>>>> When constructing Dom0 in Xen, save these values. Then Dom0 could get
>>>> them through hypercall HVMOP_get_param.
>>>>
>>>> 4. Map MMIO regions
>>>> -------------------
>>>> Register a bus_notifier for platform and amba bus in Linux. Add a new
>>>> XENMAPSPACE "XENMAPSPACE_dev_mmio". Within the register, check if the
>>>> device is newly added, then call hypercall XENMEM_add_to_physmap to map
>>>> the mmio regions.
>>>>
>>>> 5. Route device interrupts to Dom0
>>>> ----------------------------------
>>>> Route all the SPI interrupts to Dom0 before Dom0 booting.
>>>
>>> Not all the SPI will be routed to DOM0. Some are used by Xen and should
>>> never be used by any guest. I have in mind the UART and SMMU interrupts.
>>>
>>> You will have to find away to skip them nicely. Note that not all the
>>> IRQs used by Xen are properly registered when we build DOM0 (see the SMMU).
>>>
>> To uart, we can get the interrupt information from SPCR table and hide
>> it from Dom0.
> 
> Can you clarify your meaning of "hide from DOM0"? Did you mean avoid to
> route the SPI to DOM0?
> 
Yes.

>> IIUC, currently Xen (as well as Linux) doesn't support use SMMU when
>> booting with ACPI. When it supports, it could read the interrupts
>> information from IORT table and Hide them from Dom0.
> 
> Well for Xen we don't even have ACPI supported upstream ;). For Linux
> there is some on-going work. Anyway, this is not important right now.
> 

Yeah, that could be done after this patchset upstream.

Thanks,
-- 
Shannon


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