Re: [PATCH V2] Introduce a new flag for piix to disable root bus PCI hotplug

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 11 Aug 2020 18:42:08 +0530
Ani Sinha <ani@anisinha.ca> wrote:

> We introduce a new global flag for PIIX with which we can turn on or off PCI
> device hotplug on the root bus. This flag can be used to prevent all PCI
> devices from getting hotplugged or unplugged from the root PCI bus.

Tested-by: Igor Mammedov <imammedo@redhat.com>

somewhere in intial versions there were mentionig why we are doing it
(i.e for Windows sake because ...)
I suggest to add it to commit message so reason for this won't be lost.
Also giving example how to use option in commit message would be good.

with this changes:
Reviewed-by: Igor Mammedov <imammedo@redhat.com>



> 
> Signed-off-by: Ani Sinha <ani@anisinha.ca>
> ---
>  hw/acpi/piix4.c      |  3 +++
>  hw/i386/acpi-build.c | 20 ++++++++++++++++----
>  2 files changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
> index 26bac4f..94ec35a 100644
> --- a/hw/acpi/piix4.c
> +++ b/hw/acpi/piix4.c
> @@ -78,6 +78,7 @@ typedef struct PIIX4PMState {
>  
>      AcpiPciHpState acpi_pci_hotplug;
>      bool use_acpi_hotplug_bridge;
> +    bool use_acpi_root_pci_hotplug;
>  
>      uint8_t disable_s3;
>      uint8_t disable_s4;
> @@ -635,6 +636,8 @@ static Property piix4_pm_properties[] = {
>      DEFINE_PROP_UINT8(ACPI_PM_PROP_S4_VAL, PIIX4PMState, s4_val, 2),
>      DEFINE_PROP_BOOL("acpi-pci-hotplug-with-bridge-support", PIIX4PMState,
>                       use_acpi_hotplug_bridge, true),
> +    DEFINE_PROP_BOOL("acpi-root-pci-hotplug", PIIX4PMState,
> +                     use_acpi_root_pci_hotplug, true),
>      DEFINE_PROP_BOOL("memory-hotplug-support", PIIX4PMState,
>                       acpi_memory_hotplug.is_enabled, true),
>      DEFINE_PROP_END_OF_LIST(),
> diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> index b7bcbbb..a82e5c1 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -95,6 +95,7 @@ typedef struct AcpiPmInfo {
>      bool s3_disabled;
>      bool s4_disabled;
>      bool pcihp_bridge_en;
> +    bool pcihp_root_en;
>      uint8_t s4_val;
>      AcpiFadtData fadt;
>      uint16_t cpu_hp_io_base;
> @@ -245,6 +246,9 @@ static void acpi_get_pm_info(MachineState *machine, AcpiPmInfo *pm)
>      pm->pcihp_bridge_en =
>          object_property_get_bool(obj, "acpi-pci-hotplug-with-bridge-support",
>                                   NULL);
> +    pm->pcihp_root_en =
> +        object_property_get_bool(obj, "acpi-root-pci-hotplug", NULL);
> +
>  }
>  
>  static void acpi_get_misc_info(AcpiMiscInfo *info)
> @@ -337,12 +341,15 @@ static void build_append_pcihp_notify_entry(Aml *method, int slot)
>  }
>  
>  static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
> -                                         bool pcihp_bridge_en)
> +                                         bool pcihp_bridge_en,
> +                                         bool pcihp_root_en)
>  {
>      Aml *dev, *notify_method = NULL, *method;
>      QObject *bsel;
>      PCIBus *sec;
>      int i;
> +    bool root_bus = pci_bus_is_root(bus);
> +    bool root_pcihp_disabled = (root_bus && !pcihp_root_en);
>  
>      bsel = object_property_get_qobject(OBJECT(bus), ACPI_PCIHP_PROP_BSEL, NULL);
>      if (bsel) {
> @@ -361,6 +368,9 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
>          bool bridge_in_acpi;
>  
>          if (!pdev) {
> +            /* skip if pci hotplug for the root bus is disabled */
> +            if (root_pcihp_disabled)
> +                continue;
>              if (bsel) { /* add hotplug slots for non present devices */
>                  dev = aml_device("S%.02X", PCI_DEVFN(slot, 0));
>                  aml_append(dev, aml_name_decl("_SUN", aml_int(slot)));
> @@ -419,7 +429,7 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
>              method = aml_method("_S3D", 0, AML_NOTSERIALIZED);
>              aml_append(method, aml_return(aml_int(s3d)));
>              aml_append(dev, method);
> -        } else if (hotplug_enabled_dev) {
> +        } else if (hotplug_enabled_dev && !root_pcihp_disabled) {
>              /* add _SUN/_EJ0 to make slot hotpluggable  */
>              aml_append(dev, aml_name_decl("_SUN", aml_int(slot)));
>  
> @@ -439,7 +449,8 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
>               */
>              PCIBus *sec_bus = pci_bridge_get_sec_bus(PCI_BRIDGE(pdev));
>  
> -            build_append_pci_bus_devices(dev, sec_bus, pcihp_bridge_en);
> +            build_append_pci_bus_devices(dev, sec_bus, pcihp_bridge_en,
> +                                         pcihp_root_en);
>          }
>          /* slot descriptor has been composed, add it into parent context */
>          aml_append(parent_scope, dev);
> @@ -1818,7 +1829,8 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
>          if (bus) {
>              Aml *scope = aml_scope("PCI0");
>              /* Scan all PCI buses. Generate tables to support hotplug. */
> -            build_append_pci_bus_devices(scope, bus, pm->pcihp_bridge_en);
> +            build_append_pci_bus_devices(scope, bus, pm->pcihp_bridge_en,
> +                                         pm->pcihp_root_en);
>  
>              if (TPM_IS_TIS_ISA(tpm)) {
>                  if (misc->tpm_version == TPM_VERSION_2_0) {