Re: OVMF and PCI0 UID

[vit9696 <vit9696@protonmail.com>]

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Thank you, we will provide an update whether this solves the problem.

Besides, this is not the only case where UIDs are wrong for the PCI bus. In hw/arm/virt-acpi-build.c there is the following code:

    Aml *dev = aml_device("%s", "PCI0");
    aml_append(dev, aml_name_decl("_HID", aml_string("PNP0A08")));
    aml_append(dev, aml_name_decl("_CID", aml_string("PNP0A03")));
    aml_append(dev, aml_name_decl("_SEG", aml_int(0)));
    aml_append(dev, aml_name_decl("_BBN", aml_int(0)));
    aml_append(dev, aml_name_decl("_ADR", aml_int(0)));
    aml_append(dev, aml_name_decl("_UID", aml_string("PCI0")));
    aml_append(dev, aml_name_decl("_STR", aml_unicode("PCIe 0 Device")));
    aml_append(dev, aml_name_decl("_CCA", aml_int(1)));

https://github.com/qemu/qemu/blob/2c1fb4d/hw/arm/virt-acpi-build.c#L168-L175 <https://github.com/qemu/qemu/blob/2c1fb4d/hw/arm/virt-acpi-build.c#L168-L175>

It makes UID on ARM builds a string, which is certainly not expected. We do not have ARM test setups, but I hope this can be useful too.

Best wishes,
Vitaly

> 21 июля 2020 г., в 09:58, Michael S. Tsirkin <mst@redhat.com> написал(а):
> 
> 
> On Mon, Jul 20, 2020 at 11:25:58PM +0200, Laszlo Ersek wrote:
>> Hi Vitaly,
>> 
>> adding Igor, Michael, Marcel, and qemu-devel.
>> 
>> On 07/20/20 11:06, vit9696 wrote:
>>> Hello,
>>> 
>>> I discovered an issue with inconsistent QEMU/OVMF device paths, and
>>> while I am unsure whether directing this e-mail is appropriate to you,
>>> I believe that you likely have the contacts you could forward this
>>> e-mail to.
>>> 
>>> macOS uses ACPI UIDs to build the DevicePath for NVRAM boot options,
>>> while OVMF firmware gets them via an internal channel through QEMU.
>>> Due to a bug in QEMU (or OVMF) currently UEFI firmware and ACPI have
>>> different values, and this makes the underlying operating system
>>> unable to report its boot option.
>>> 
>>> The particular node in question is the primary PciRoot (PCI0 in ACPI),
>>> which for some reason gets assigned 1 in ACPI UID and 0 in the
>>> DevicePath. To me this looks like a bug here:
>>> https://github.com/qemu/qemu/blob/8f06f22/hw/i386/acpi-build.c#L1511-L1515
>>> Which does not correspond to the primary PCI identifier here:
>>> https://github.com/qemu/qemu/blob/5a79d10/hw/pci/pci.c#L160-L162
>>> 
>>> Reference with the device paths, OVMF startup logs, and ACPI table
>>> dumps (SysReport):
>>> https://github.com/acidanthera/bugtracker/issues/1050
>>> 
>>> Would you be able to forward this to the right people or perhaps keep
>>> an eye on the issue itself?
>> 
>> I think you are right.
>> 
>> In UEFI v2.8, section "10.4.2 Rules with ACPI _HID and _UID" ends with
>> the paragraph,
>> 
>>    Root PCI bridges will use the plug and play ID of PNP0A03, This will
>>    be stored in the ACPI Device Path _HID field, or in the Expanded
>>    ACPI Device Path _CID field to match the ACPI name space. The _UID
>>    in the ACPI Device Path structure must match the _UID in the ACPI
>>    name space.
>> 
>> (See especially the last sentence.)
>> 
>> Considering *extra* root bridges / root buses (with bus number > 0),
>> QEMU's ACPI generator actually does the right thing; since QEMU commit
>> c96d9286a6d7 ("i386/acpi-build: more traditional _UID and _HID for PXB
>> root buses", 2015-06-11).
>> 
>> However, the _UID values for root bridge zero (on both i440fx and q35)
>> have always been "wrong" (from UEFI perspective), going back in QEMU to
>> commit 74523b850189 ("i386: add ACPI table files from seabios",
>> 2013-10-14).
>> 
>> Even in SeaBIOS, these _UID values have always been 1; see commit
>> a4d357638c57 ("Port rombios32 code from bochs-bios.", 2008-03-08) for
>> i440fx, and commit ecbe3fd61511 ("seabios: q35: add dsdt", 2012-12-01)
>> for q35.
>> 
>> Does the following patch work for you? (I can see you proposed the same
>> in
>> <https://github.com/acidanthera/bugtracker/issues/1050#issuecomment-660734139>)
>> 
>>> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
>>> index b7bcbbbb2a35..7a5a8b3521b0 100644
>>> --- a/hw/i386/acpi-build.c
>>> +++ b/hw/i386/acpi-build.c
>>> @@ -1496,9 +1496,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>>>         sb_scope = aml_scope("_SB");
>>>         dev = aml_device("PCI0");
>>>         aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A03")));
>>>         aml_append(dev, aml_name_decl("_ADR", aml_int(0)));
>>> -        aml_append(dev, aml_name_decl("_UID", aml_int(1)));
>>> +        aml_append(dev, aml_name_decl("_UID", aml_int(0)));
>>>         aml_append(sb_scope, dev);
>>>         aml_append(dsdt, sb_scope);
>>> 
>>>         build_hpet_aml(dsdt);
>>> @@ -1511,9 +1511,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>>>         dev = aml_device("PCI0");
>>>         aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A08")));
>>>         aml_append(dev, aml_name_decl("_CID", aml_eisaid("PNP0A03")));
>>>         aml_append(dev, aml_name_decl("_ADR", aml_int(0)));
>>> -        aml_append(dev, aml_name_decl("_UID", aml_int(1)));
>>> +        aml_append(dev, aml_name_decl("_UID", aml_int(0)));
>>>         aml_append(dev, build_q35_osc_method());
>>>         aml_append(sb_scope, dev);
>>>         aml_append(dsdt, sb_scope);
>> 
>> If it does, I suggest submitting the above patch to qemu-devel, and/or
>> filing a bug for upstream QEMU at <https://bugs.launchpad.net/qemu/>.
> 
> Or even just reporting whether the above helps you, we can
> take it from there.
> 
>> (Note: I didn't even compile the above change.)
>> 
>> Thanks
>> Laszlo


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