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

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 8 Jan 2016 12:21:09 +0800
Xiao Guangrong <guangrong.xiao@linux.intel.com> wrote:

> 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.
For SeaBIOS it's so for now.