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

[Peter Maydell <peter.maydell@linaro.org>]

On 16 January 2017 at 17:30, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> On 16 January 2017 at 17:25, Peter Maydell <peter.maydell@linaro.org> wrote:
>> On 13 January 2017 at 17:32, Ard Biesheuvel <ard.biesheuvel@linaro.org> 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 <ard.biesheuvel@linaro.org>
>>> ---
>>>  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?

Because the "virt-2.8" machine has to present to the guest
exactly what "virt" did as of the QEMU 2.8 release, including
any bugs or missing things we happened to have in our ACPI
tables. This allows cross-version compatibility (including
VM migration). Drew will have a more detailed explanation
if you need it.

thanks
-- PMM