Re: [RFC PATCH] hw/acpi: do not let OSPM set pcie native hotplug when acpi hotplug is enabled

[Ani Sinha]

On Mon, 5 Sep 2022, Ani Sinha wrote:

>
>

> > >
> > > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > > index 0355bd3dda..3dc9379f27 100644
> > > --- a/hw/i386/acpi-build.c
> > > +++ b/hw/i386/acpi-build.c
> > > @@ -1348,10 +1348,12 @@ static Aml *build_q35_osc_method(bool 
> > > enable_native_pcie_hotplug)
> > >  {
> > >      Aml *if_ctx;
> > >      Aml *if_ctx2;
> > > +    Aml *if_ctx3;
> > >      Aml *else_ctx;
> > >      Aml *method;
> > >      Aml *a_cwd1 = aml_name("CDW1");
> > >      Aml *a_ctrl = aml_local(0);
> > > +    Aml *a_pcie_nhp_ctl = aml_local(1);
> > >
> > >      method = aml_method("_OSC", 4, AML_NOTSERIALIZED);
> > >      aml_append(method, aml_create_dword_field(aml_arg(3), aml_int(0), 
> > > "CDW1"));
> > > @@ -1366,11 +1368,26 @@ static Aml *build_q35_osc_method(bool 
> > > enable_native_pcie_hotplug)
> > >      /*
> > >       * Always allow native PME, AER (no dependencies)
> > >       * Allow SHPC (PCI bridges can have SHPC controller)
> > > -     * Disable PCIe Native Hot-plug if ACPI PCI Hot-plug is enabled.
> > >       */
> > > -    aml_append(if_ctx, aml_and(a_ctrl,
> > > -        aml_int(0x1E | (enable_native_pcie_hotplug ? 0x1 : 0x0)), 
> > > a_ctrl));
> > > +    aml_append(if_ctx, aml_and(a_ctrl, aml_int(0x1F), a_ctrl));
> >
> > that makes us not actually mask any capabilities since you forgot to mask
> > bit 1 later under if_ctx3 context.
> >
> > So OSPM will see a permanent failure (_OSC failure bit in CWD1)
> > and will have no idea that PCI Hotplug is not supported since we return CWD3
> > with this bit still set whoever much it tries to negotiate.
>
> The failure is only returned when the OS requests/probes native hotplug
> capability in CWD1.

I meant CWD3.