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

[Ani Sinha]

On Wed, Aug 19, 2020 at 3:30 PM Igor Mammedov <imammedo@redhat.com> wrote:
>
> 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>

Thanks Igor, I have sent a V4 with your suggestions to the commit
message and some more
rework on the patch. The V4 has again been tested by me in the same
setup. Looks good so far.

>
>
>
> >
> > 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) {
>