Re: [PATCH v3 07/10] hw/i386: declare ACPI mother board resource for MMCONFIG region

[Igor Mammedov]

On Tue, 16 Feb 2021 10:13:25 -0800
Isaku Yamahata <isaku.yamahata@gmail.com> wrote:

> On Tue, Feb 16, 2021 at 08:45:48AM -0500,
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > On Tue, Feb 16, 2021 at 01:43:01AM -0800, Isaku Yamahata wrote:  
> > > On Mon, Feb 15, 2021 at 01:48:32PM +0100,
> > > Igor Mammedov <imammedo@redhat.com> wrote:
> > >   
> > > > On Fri, 12 Feb 2021 12:51:57 -0800
> > > > Isaku Yamahata <isaku.yamahata@gmail.com> wrote:
> > > >   
> > > > > On Fri, Feb 12, 2021 at 04:40:38PM +0100,
> > > > > Igor Mammedov <imammedo@redhat.com> wrote:
> > > > >   
> > > > > > On Wed, 10 Feb 2021 22:46:43 -0800
> > > > > > Isaku Yamahata <isaku.yamahata@intel.com> wrote:
> > > > > >     
> > > > > > > +    Aml *dev;
> > > > > > > +    Aml *rbuf;
> > > > > > > +    Aml *resource_template;
> > > > > > > +    Aml *rbuf_name;
> > > > > > > +    Aml *crs;
> > > > > > > +
> > > > > > > +    if (!acpi_get_mcfg(&mcfg)) {
> > > > > > > +        return NULL;
> > > > > > > +    }
> > > > > > > +
> > > > > > > +    /* DRAM controller */
> > > > > > > +    dev = aml_device("DRAC");
> > > > > > > +    aml_append(dev, aml_name_decl("_HID", 
> > > > > > > aml_string("PNP0C01")));
> > > > > > > +
> > > > > > > +    resource_template = aml_resource_template();
> > > > > > > +    aml_append(resource_template,
> > > > > > > +               aml_qword_memory(AML_POS_DECODE,
> > > > > > > +                                AML_MIN_FIXED,
> > > > > > > +                                AML_MAX_FIXED,
> > > > > > > +                                AML_NON_CACHEABLE,
> > > > > > > +                                AML_READ_WRITE,
> > > > > > > +                                0x0000000000000000,
> > > > > > > +                                mcfg.base,
> > > > > > > +                                mcfg.base + mcfg.size - 1,    
> > > > > > s/mcfg.base + mcfg.size - 1/mcfg.base/    
> > > > > 
> > > > > AddressMaximum needs to be the highest address of the region.
> > > > > Not base address. By disassemble/assembl it, iasl complains as 
> > > > > follows.
> > > > > Also there are similar examples in acpi-build.c.  
> > > > I mostly clean up all places to use the same base address for min/max,
> > > > but probably something were left behind.
> > > > 
> > > > spec says:
> > > > 
> > > > acpi 6.3: 19.6.110 QWordMemory
> > > > 
> > > > AddressMaximum evaluates to a 64-bit integer that specifies the highest 
> > > > possible base address of the
> > > > Memory range. The value must have ‘0’ in all bits where the 
> > > > corresponding bit in AddressGranularity is
> > > > ‘1’. For bridge devices which translate addresses, this is the address 
> > > > on the secondary bus. The 64-bit
> > > > field DescriptorName ._MAX is automatically created to refer to this 
> > > > portion of the resource descriptor.  
> > > 
> > > Ok, Linux guest is happy with min=max.
> > > I conlude that it's iasl issue.
> > > 
> > > Thanks,  
> > 
> > OK but what about all the other places in the code that seem to use this
> > field differently?  
> 
> Igor, what do you think?
> The followings are the summary of the situation.
> 
> - acpi 6.4: 19.6.110 QWordMemory
>   _MAX: maximum of base address.
> 
> - acpi 6.4: 6.4.3.5 Address Space Resource Descriptors
>   table 6.44
>   If _LEN > 0 and _MIF = 1 and _MAF = 1, then _LEN = _MAX - _MIN + 1
>   This doesn't match with the above description
I'd say it 19.6.110 doesn't describes whole possibilities of resource,
but only subset in its current phrasing.

> - iasl
>   If _LEN > 0 and _MIF = 1 and _MAF = 1,
>   it emits warning on _LEN != _MAX - _MIN + 1
so IASL is right and follows spec.

Anyways, My apologies for misleading and your patch is correct.

I need to add similar checks to QEMU code plus comments to avoid confusion
in future.

> - Linux Guest MMCONFIG check 
>   check_mcfg_resoure() uses only _MIN. doesn't use _MAX.
>   _MAX value doesn't matter
> 
> - Linux acpi code
>   acpi_decode_space() uses _MAX to calulate range [start, end], not use _LEN.
>   i.e. It assumes _LEN = _MAX - _MIN + 1 if _LEN > 0, _MIF = 1, _MAF = 1
> 
> - qemu code sets for [qd]word_memory_resource (except this patch)
>   If _LEN > 0 and _MIF = 1 and _MAF = 1, then set _LEN = _MAX - _MIN + 1