Re: [PATCH 1/2] i386/acpi: fix inconsistent QEMU/OVMF device paths

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jul 30, 2020 at 06:11:17PM +0200, Philippe Mathieu-Daudé wrote:
> On 7/30/20 5:58 PM, Michael S. Tsirkin wrote:
> > 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 ACPI 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. This is due to the _UID assigned to it by build_dsdt in
> > hw/i386/acpi-build.c Which does not correspond to the primary PCI
> > identifier given by pcibus_num in hw/pci/pci.c
> > 
> > Reference with the device paths, OVMF startup logs, and ACPI table
> > dumps (SysReport):
> > https://github.com/acidanthera/bugtracker/issues/1050
> > 
> > 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.
> > 
> > Suggested-by: Laszlo Ersek <lersek@redhat.com>
> > Tested-by: vit9696 <vit9696@protonmail.com>
> 
> Vitaly uses his full name on EDK2 mailing list, so I don't think he'll
> have a problem to use it in QEMU too:
> Tested-by: Vitaly Cheptsov <vit9696@protonmail.com>
> 
> From:
> https://wiki.qemu.org/Contribute/SubmitAPatch#Patch_emails_must_include_a_Signed-off-by:_line
> "Please use your real name to sign a patch (not an alias or acronym)."

Right. Tested-by is different though, I don't think we have
a problem with anonymous testing.

Anyway, updated.

> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  hw/i386/acpi-build.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > index b7bcbbbb2a..7a5a8b3521 100644
> > --- a/hw/i386/acpi-build.c
> > +++ b/hw/i386/acpi-build.c
> > @@ -1497,7 +1497,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
> >          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);
> >  
> > @@ -1512,7 +1512,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
> >          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);
> >