Re: [PATCH] Introduce global piix flag to disable PCI hotplug

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

On Mon, Aug 10, 2020 at 04:59:41PM +0530, Ani Sinha wrote:
> We introduce a new global flag for PIIX with which we can
> turn on or off PCI device hotplug. This flag can be used
> to prevent all PCI devices from getting hotplugged/unplugged
> on the PCI bus. The new options disables all hotpluh HW
> initialization code as well as the ACPI AMLs.
> 
> Signed-off-by: Ani Sinha <ani@anisinha.ca>

Well we have a flag like this for pci bridges, right?
So all that's left is an option to disable hotplug
for the pci root, right?
Wouldn't that be better than disabling it globally?

> ---
>  hw/acpi/piix4.c      |  8 ++++++--
>  hw/i386/acpi-build.c | 20 ++++++++++++++------
>  2 files changed, 20 insertions(+), 8 deletions(-)
> 
> diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
> index 26bac4f..8b13e86 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_pci_hotplug;
>  
>      uint8_t disable_s3;
>      uint8_t disable_s4;
> @@ -595,8 +596,9 @@ static void piix4_acpi_system_hot_add_init(MemoryRegion *parent,
>                            "acpi-gpe0", GPE_LEN);
>      memory_region_add_subregion(parent, GPE_BASE, &s->io_gpe);
>  
> -    acpi_pcihp_init(OBJECT(s), &s->acpi_pci_hotplug, bus, parent,
> -                    s->use_acpi_hotplug_bridge);
> +    if (s->use_acpi_pci_hotplug)
> +        acpi_pcihp_init(OBJECT(s), &s->acpi_pci_hotplug, bus, parent,
> +                        s->use_acpi_hotplug_bridge);
>  
>      s->cpu_hotplug_legacy = true;
>      object_property_add_bool(OBJECT(s), "cpu-hotplug-legacy",
> @@ -635,6 +637,8 @@ 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-pci-hotplug", PIIX4PMState,
> +                     use_acpi_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..343b9b6 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_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_en =
> +        object_property_get_bool(obj, "acpi-pci-hotplug", NULL);
> +
>  }
>  
>  static void acpi_get_misc_info(AcpiMiscInfo *info)
> @@ -337,14 +341,16 @@ 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_en)
>  {
>      Aml *dev, *notify_method = NULL, *method;
> -    QObject *bsel;
> +    QObject *bsel = NULL;
>      PCIBus *sec;
>      int i;
>  
> -    bsel = object_property_get_qobject(OBJECT(bus), ACPI_PCIHP_PROP_BSEL, NULL);
> +    if (pcihp_en)
> +        bsel = object_property_get_qobject(OBJECT(bus),
> +                                           ACPI_PCIHP_PROP_BSEL, NULL);
>      if (bsel) {
>          uint64_t bsel_val = qnum_get_uint(qobject_to(QNum, bsel));
>  
> @@ -439,7 +445,8 @@ 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_en);
>          }
>          /* slot descriptor has been composed, add it into parent context */
>          aml_append(parent_scope, dev);
> @@ -468,7 +475,7 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
>      }
>  
>      /* Notify about child bus events in any case */
> -    if (pcihp_bridge_en) {
> +    if (pcihp_bridge_en && pcihp_en) {
>          QLIST_FOREACH(sec, &bus->child, sibling) {
>              int32_t devfn = sec->parent_dev->devfn;
>  
> @@ -1818,7 +1825,8 @@ 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_en);
>  
>              if (TPM_IS_TIS_ISA(tpm)) {
>                  if (misc->tpm_version == TPM_VERSION_2_0) {
> -- 
> 2.7.4