Re: [Qemu-devel] [PATCH v2] hw/arm/virt-acpi - reserve ECAM space as PNP0C02 device

[Ard Biesheuvel]

On 16 January 2017 at 17:25, Peter Maydell <address@hidden> wrote:
> On 13 January 2017 at 17:32, Ard Biesheuvel <address@hidden> wrote:
>> Linux for arm64 v4.10 and later will complain if the ECAM config space is
>> not reserved in the ACPI namespace:
>>
>>   acpi PNP0A08:00: [Firmware Bug]: ECAM area [mem 0x3f000000-0x3fffffff] not 
>> reserved in ACPI namespace
>>
>> The rationale is that OSes that don't consume the MCFG table should still
>> be able to infer that the PCI config space MMIO region is occupied.
>>
>> So update the ACPI table generation routine to add this reservation.
>>
>> Signed-off-by: Ard Biesheuvel <address@hidden>
>> ---
>>  hw/arm/virt-acpi-build.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
>> index 085a61117378..50d52f685f68 100644
>> --- a/hw/arm/virt-acpi-build.c
>> +++ b/hw/arm/virt-acpi-build.c
>> @@ -310,6 +310,13 @@ static void acpi_dsdt_add_pci(Aml *scope, const 
>> MemMapEntry *memmap,
>>      Aml *dev_rp0 = aml_device("%s", "RP0");
>>      aml_append(dev_rp0, aml_name_decl("_ADR", aml_int(0)));
>>      aml_append(dev, dev_rp0);
>> +
>> +    Aml *dev_res0 = aml_device("%s", "RES0");
>> +    aml_append(dev_res0, aml_name_decl("_HID", aml_string("PNP0C02")));
>> +    crs = aml_resource_template();
>> +    aml_append(crs, aml_memory32_fixed(base_ecam, size_ecam, 
>> AML_READ_WRITE));
>> +    aml_append(dev_res0, aml_name_decl("_CRS", crs));
>> +    aml_append(dev, dev_res0);
>>      aml_append(scope, dev);
>>  }
>
> This needs to be controlled via the machine class back-compat
> machinery in hw/arm/virt.c so that it only happens for virt-2.9
> and later.
>

Why exactly?