Re: [Qemu-devel] How to reserve guest physical region for ACPI

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

On 01/07/2016 05:21 PM, Igor Mammedov wrote:
> On Wed, 6 Jan 2016 01:07:45 +0800
> Xiao Guangrong <guangrong.xiao@linux.intel.com> wrote:
>
>> On 01/06/2016 12:43 AM, Michael S. Tsirkin wrote:
>>
>>>>> Yes - if address is static, you need to put it outside
>>>>> the table. Can come right before or right after this.
>>>>>
>>>>>> Also if OperationRegion() is used, then one has to patch
>>>>>> DefOpRegion directly as RegionOffset must be Integer,
>>>>>> using variable names is not permitted there.
>>>>>
>>>>> I am not sure the comment was understood correctly.
>>>>> The comment says really "we can't use DataTableRegion
>>>>> so here is an alternative".
>>>> so how are you going to access data at which patched
>>>> NameString point to?
>>>> for that you'd need a normal patched OperationRegion
>>>> as well since DataTableRegion isn't usable.
>>>
>>> For VMGENID you would patch the method that
>>> returns the address - you do not need an op region
>>> as you never access it.
>>>
>>> I don't know about NVDIMM. Maybe OperationRegion can
>>> use the patched NameString? Will need some thought.
>>
>> The ACPI spec says that the offsetTerm in OperationRegion
>> is evaluated as Int, so the named object is allowed to be
>> used in OperationRegion, that is exact what my patchset
>> is doing (http://marc.info/?l=kvm&m=145193395624537&w=2):
> that's not my reading of spec:
> "
> DefOpRegion := OpRegionOp NameString RegionSpace RegionOffset RegionLen
> RegionOffset := TermArg => Integer
> TermArg := Type2Opcode | DataObject | ArgObj | LocalObj
> "
>
> Named object is not allowed per spec, but you've used ArgObj which is
> allowed, even Windows ok with such dynamic OperationRegion.

Sorry, Named object i was talking about is something like this:
Name("SOTH", int(0x10000))

I am checking acpi spec, and this is a formal NamedObj definition in
that spec, my fault.

>
>>
>> +    dsm_mem = aml_arg(3);
>> +    aml_append(method, aml_store(aml_call0(NVDIMM_GET_DSM_MEM), dsm_mem));
>>
>> +    aml_append(method, aml_operation_region("NRAM", AML_SYSTEM_MEMORY,
>> +                                            dsm_mem, TARGET_PAGE_SIZE));
>>
>> We hide the int64 object which is patched by BIOS in the method,
>> NVDIMM_GET_DSM_MEM, to make windows XP happy.
> considering that NRAM is allocated in low mem it's even fine to move
> OperationRegion into object scope to get rid of IASL warnings
> about declariong Named object inside method, but the you'd need to
> patch it directly as the only choice for RegionOffset would be DataObject
>

Yes, it is. So it is depends on the question in my reply of another thread:
http://marc.info/?l=kvm&m=145222487605390&w=2
Can we assume that BIOS allocated address is always 32 bits?

If yes, we also need not make ssdt as v2.