Re: [PATCH V2] Add a new PIIX option to control PCI hot unplugging of devices on non-root buses

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Apr 28, 2020 at 12:05:47PM -0400, Michael S. Tsirkin wrote:
> On Tue, Apr 28, 2020 at 10:16:52AM +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.
> > 
> > It has been tested on Windows guests.
> > 
> > Signed-off-by: Ani Sinha <ani.sinha@nutanix.com>
> 
> It's still a non starter until we find something similar for PCIE and
> SHPC. Do guests check command status? Can some unplug commands fail?

Why does PCIE need anything ? For that we already have ability to
control hotplugging per-slot in pcie-root-port.  If SHPC doesn't
support this that's fine too, it isn't a reason to block its merge
and use with x86 i440fx machine.

> 
> 
> > ---
> >  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 964d6f5..59fa707 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_pci_hotplug;
> > +    bool use_acpi_unplug;
> >  
> >      uint8_t disable_s3;
> >      uint8_t disable_s4;
> > @@ -633,6 +634,8 @@ 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 23c77ee..71b3ac3 100644
> > --- a/hw/i386/acpi-build.c
> > +++ b/hw/i386/acpi-build.c
> > @@ -96,6 +96,7 @@ 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;
> > @@ -240,6 +241,9 @@ 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->pcihup_bridge_en =
> > +        object_property_get_bool(obj, "acpi-pci-hotunplug-enable-bridge",
> > +                                 NULL);
> >  }
> >  
> >  static void acpi_get_misc_info(AcpiMiscInfo *info)
> > @@ -451,7 +455,8 @@ 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;
> > @@ -479,11 +484,14 @@ 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);
> > @@ -537,12 +545,14 @@ 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);
> >              }
> > @@ -553,7 +563,8 @@ 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);
> > @@ -2196,7 +2207,8 @@ 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_ISA(tpm)) {
> >                  if (misc->tpm_version == TPM_VERSION_2_0) {
> > -- 
> > 1.9.4
> 
> 

Regards,
Daniel
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