Re: [RFC PATCH v2 3/4] hw/i386/acpi-build: Turn off support of PCIe native hot-plug and SHPC in _OSC

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 18 Aug 2020 23:52:26 +0200
Julia Suvorova <jusual@redhat.com> wrote:

> Other methods may be used if the system is capable of this and the _OSC bit
> is set. Disable them explicitly to force ACPI PCI hot-plug use. The older
> versions will still use PCIe native.
> 
> Signed-off-by: Julia Suvorova <jusual@redhat.com>
> ---
>  hw/i386/acpi-build.h | 11 +++++++++++
>  hw/i386/acpi-build.c | 21 +++++++++++++++------
>  2 files changed, 26 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/i386/acpi-build.h b/hw/i386/acpi-build.h
> index 74df5fc612..6f94312c39 100644
> --- a/hw/i386/acpi-build.h
> +++ b/hw/i386/acpi-build.h
> @@ -5,6 +5,17 @@
>  
>  extern const struct AcpiGenericAddress x86_nvdimm_acpi_dsmio;
>  
> +/* PCI Firmware Specification 3.2, Table 4-5 */
> +typedef enum {
> +    ACPI_OSC_NATIVE_HP_EN = 0,
> +    ACPI_OSC_SHPC_EN = 1,
> +    ACPI_OSC_PME_EN = 2,
> +    ACPI_OSC_AER_EN = 3,
> +    ACPI_OSC_PCIE_CAP_EN = 4,
> +    ACPI_OSC_LTR_EN = 5,
> +    ACPI_OSC_ALLONES_INVALID = 6,
> +} AcpiOSCField;
> +
>  void acpi_setup(void);
>  
>  #endif
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index f3cd52bd06..c5f4802b8c 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -1411,7 +1411,7 @@ static void build_i386_pci_hotplug(Aml *table, uint64_t pcihp_addr)
>      aml_append(table, scope);
>  }
>  
> -static Aml *build_q35_osc_method(void)
> +static Aml *build_q35_osc_method(AcpiPmInfo *pm)
>  {
>      Aml *if_ctx;
>      Aml *if_ctx2;
> @@ -1419,6 +1419,7 @@ static Aml *build_q35_osc_method(void)
>      Aml *method;
>      Aml *a_cwd1 = aml_name("CDW1");
>      Aml *a_ctrl = aml_local(0);
> +    unsigned osc_ctrl;
>  
>      method = aml_method("_OSC", 4, AML_NOTSERIALIZED);
>      aml_append(method, aml_create_dword_field(aml_arg(3), aml_int(0), "CDW1"));
> @@ -1430,11 +1431,19 @@ static Aml *build_q35_osc_method(void)
>  
>      aml_append(if_ctx, aml_store(aml_name("CDW3"), a_ctrl));
>  
> +    /* Always allow native PME, AER (depend on PCIE Capability Control) */
> +    osc_ctrl = BIT(ACPI_OSC_PME_EN) | BIT(ACPI_OSC_AER_EN) |
> +               BIT(ACPI_OSC_PCIE_CAP_EN);
> +
>      /*
> -     * Always allow native PME, AER (no dependencies)
> -     * Allow SHPC (PCI bridges can have SHPC controller)
> +     * Guests seem to generally prefer native hot-plug control.
> +     * Enable it only when we do not use ACPI hot-plug.
>       */
> -    aml_append(if_ctx, aml_and(a_ctrl, aml_int(0x1F), a_ctrl));
> +    if (!pm->pcihp_bridge_en) {
> +        osc_ctrl |= BIT(ACPI_OSC_NATIVE_HP_EN) | BIT(ACPI_OSC_SHPC_EN);
> +    }

ACPI hotplug works only for coldplugged bridges, and native one is used
on hotplugged ones.
Wouldn't that break SHPC/Native hotplug on hotplugged PCI/PCI-E bridge?

> +    aml_append(if_ctx, aml_and(a_ctrl, aml_int(osc_ctrl), a_ctrl));
>  
>      if_ctx2 = aml_if(aml_lnot(aml_equal(aml_arg(1), aml_int(1))));
>      /* Unknown revision */
> @@ -1514,7 +1523,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>          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, build_q35_osc_method());
> +        aml_append(dev, build_q35_osc_method(pm));
>          aml_append(sb_scope, dev);
>          aml_append(dsdt, sb_scope);
>  
> @@ -1590,7 +1599,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>              if (pci_bus_is_express(bus)) {
>                  aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A08")));
>                  aml_append(dev, aml_name_decl("_CID", aml_eisaid("PNP0A03")));
> -                aml_append(dev, build_q35_osc_method());
> +                aml_append(dev, build_q35_osc_method(pm));
>              } else {
>                  aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A03")));
>              }