Re: [PATCH] Add a new PIIX option to control PCI hot unplugging of devices on non-root buses

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

On Fri, Apr 17, 2020 at 03:13:31PM +0000, Ani Sinha wrote:
> A new option "use_acpi_unplug" is introduced for PIIX which will
> selectively only disable hot unplugging of both hot plugged and
> cold plugged PCI devices on non-root PCI buses. This will prevent
> hot unplugging of devices from Windows based guests from system
> tray but will not prevent devices from being hot plugged into the
> guest.
> 
> The patch is initial version and is a rough implementation. It has
> been tested on Windows guests.
> 
> Signed-off-by: Ani Sinha <ani.sinha@nutanix.com>

Is there a real reason to do this? Can't we just limit the
hotplug control to pcie ports? At some point I'd like us to
start leaving piix alone...


> ---
>  hw/acpi/piix4.c      |  3 +++
>  hw/i386/acpi-build.c | 40 ++++++++++++++++++++++++++--------------
>  2 files changed, 29 insertions(+), 14 deletions(-)
> 
> diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
> index d706360..dad1bf4 100644
> --- a/hw/acpi/piix4.c
> +++ b/hw/acpi/piix4.c
> @@ -82,6 +82,7 @@ typedef struct PIIX4PMState {
>  
>      AcpiPciHpState acpi_pci_hotplug;
>      bool use_acpi_pci_hotplug;
> +    bool use_acpi_unplug;
>  
>      uint8_t disable_s3;
>      uint8_t disable_s4;
> @@ -676,6 +677,8 @@ 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_pci_hotplug, true),
> +    DEFINE_PROP_BOOL("acpi-pci-hotunplug-enable-bridge", PIIX4PMState,
> +                     use_acpi_unplug, 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 2bc8117..526feb2 100644
> --- a/hw/i386/acpi-build.c
> +++ b/hw/i386/acpi-build.c
> @@ -94,6 +94,7 @@ typedef struct AcpiPmInfo {
>      bool s3_disabled;
>      bool s4_disabled;
>      bool pcihp_bridge_en;
> +    bool pcihup_bridge_en;
>      uint8_t s4_val;
>      AcpiFadtData fadt;
>      uint16_t cpu_hp_io_base;
> @@ -220,6 +221,9 @@ static void acpi_get_pm_info(AcpiPmInfo *pm)
>      pm->pcihp_bridge_en =
>          object_property_get_bool(obj, "acpi-pci-hotplug-with-bridge-support",
>                                   NULL);
> +    pm->pcihup_bridge_en =
> +        object_property_get_bool(obj, "acpi-pci-hotunplug-enable-bridge",
> +                                 NULL);
>  }
>  
>  static void acpi_get_misc_info(AcpiMiscInfo *info)
> @@ -430,7 +434,8 @@ 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 pcihup_bridge_en)
>  {
>      Aml *dev, *notify_method = NULL, *method;
>      QObject *bsel;
> @@ -458,11 +463,14 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
>                  dev = aml_device("S%.02X", PCI_DEVFN(slot, 0));
>                  aml_append(dev, aml_name_decl("_SUN", aml_int(slot)));
>                  aml_append(dev, aml_name_decl("_ADR", aml_int(slot << 16)));
> -                method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
> -                aml_append(method,
> -                    aml_call2("PCEJ", aml_name("BSEL"), aml_name("_SUN"))
> -                );
> -                aml_append(dev, method);
> +                if (pcihup_bridge_en || pci_bus_is_root(bus)) {
> +                    method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
> +                    aml_append(method,
> +                               aml_call2("PCEJ", aml_name("BSEL"),
> +                                         aml_name("_SUN"))
> +                        );
> +                    aml_append(dev, method);
> +                }
>                  aml_append(parent_scope, dev);
>  
>                  build_append_pcihp_notify_entry(notify_method, slot);
> @@ -516,12 +524,14 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
>              /* add _SUN/_EJ0 to make slot hotpluggable  */
>              aml_append(dev, aml_name_decl("_SUN", aml_int(slot)));
>  
> -            method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
> -            aml_append(method,
> -                aml_call2("PCEJ", aml_name("BSEL"), aml_name("_SUN"))
> -            );
> -            aml_append(dev, method);
> -
> +            if (pcihup_bridge_en || pci_bus_is_root(bus)) {
> +                method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
> +                aml_append(method,
> +                           aml_call2("PCEJ", aml_name("BSEL"),
> +                                     aml_name("_SUN"))
> +                    );
> +                aml_append(dev, method);
> +            }
>              if (bsel) {
>                  build_append_pcihp_notify_entry(notify_method, slot);
>              }
> @@ -532,7 +542,8 @@ 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,
> +                                         pcihup_bridge_en);
>          }
>          /* slot descriptor has been composed, add it into parent context */
>          aml_append(parent_scope, dev);
> @@ -2133,7 +2144,8 @@ 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->pcihup_bridge_en);
>  
>              if (TPM_IS_TIS(tpm_find())) {
>                  dev = aml_device("ISA.TPM");
> -- 
> 1.9.4