Re: [Qemu-devel] [PATCH] acpi: change CPU container node _HID to compatible PNP0A05

[Evgeny Yakovlev]

On 22.05.2017 13:35, Igor Mammedov wrote:
> On Mon, 22 May 2017 12:50:30 +0300
> Evgeny Yakovlev <address@hidden> wrote:
>
> > When running windows 2016 server guests we have encountered a problem
> > with ACPI representation of CPU devices. This windows version contains a
> > hidinterrupt.sys driver which looks for ACPI device node with _HID set
> > to "ACPI0010" and "ACPI0011". ACPI0010 is also a valid id for CPU
> > container device which qemu uses.
> >
> > hidinterrupt driver takes over (even though it fails) ACPI0010 node and
> > thus hides its children -- the CPUs -- from the regular ACPI
> > enumeration.  So there are no processors in the Windows device tree
> > Device Manager or "!devnode 0 1" in the debugger.
> >
> > hidinterrupt.inf as shipped with Windows 2016 has both ACPI0011 and
> > ACPI0010; the record for the latter is preceded with a comment "This Id
> > is not to be used. It will be removed once everyone has stopped using
> > it."  So I guess the typo was not in the driver but in the ACPI tables
> > of some device(s) which the driver wanted to support despite the bug.
> >
> > For reference this is a known issue:
> > https://bugzilla.redhat.com/show_bug.cgi?id=1377155#c31
> >
> > This change works around this problem by setting qemu CPU container ACPI
> > _HID to compatible PNP0A05.
> I'd say NACK to it.
> It's Windows server 2016 bug that violates spec and
> it's been reported to them before RTM has been released.
> So complain to Microsoft support and make them fix it.
>
> Meanwhile there is MS suggested workaround to fix issue,
> one can use https://bugzilla.redhat.com/show_bug.cgi?id=1377155#c17
>
> Perhaps I should add workaround link as comment above line:
>
> aml_append(cpus_dev, aml_name_decl("_HID", aml_string("ACPI0010")));

Thanks for replying!

Strictly speaking, this is not a Windows bug. Comment in INF file says 
that they had to support a hardware device which erroneously picked this 
ACPI HID.

I understand that this is not a qemu problem either. Then again other 
emulators we've tested this on (VirtualBox, Parallels, HyperV) provide a 
compatible ACPI configuration and don't trigger this conflict. If this 
fix is not a big deal and does not affect anything negatively then maybe 
we pay a relatively small price to improve compatibility with some guest 
systems?


> > Signed-off-by: Evgeny Yakovlev <address@hidden>
> > ---
> >   hw/acpi/cpu.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
> > index a233fe1..b93db40 100644
> > --- a/hw/acpi/cpu.c
> > +++ b/hw/acpi/cpu.c
> > @@ -397,7 +397,7 @@ void build_cpus_aml(Aml *table, MachineState *machine, 
> > CPUHotplugFeatures opts,
> >           Aml *rm_evt = aml_name("%s.%s", cphp_res_path, CPU_REMOVE_EVENT);
> >           Aml *ej_evt = aml_name("%s.%s", cphp_res_path, CPU_EJECT_EVENT);
> >   
> > -        aml_append(cpus_dev, aml_name_decl("_HID", aml_string("ACPI0010")));
> > +        aml_append(cpus_dev, aml_name_decl("_HID", aml_string("PNP0A05")));
> >           aml_append(cpus_dev, aml_name_decl("_CID", aml_eisaid("PNP0A05")));
> >   
> >           method = aml_method(CPU_NOTIFY_METHOD, 2, AML_NOTSERIALIZED);