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

[Ani Sinha]

This is not a workaround, this is a feature we need badly. We have discussed this at length. Igor suggested we have one additional global flag to disable all pci hotplug. But then that leads to strange case when pci hotplug on the bridges are enabled (we have a separate flag for that). Hence, I think we can simply add another flag to disable hotplug just for the pci root bus. 

On Tue, Aug 18, 2020 at 3:46 PM Philippe Mathieu-Daudé <philmd@redhat.com> wrote:

Hi,



On 8/18/20 11:54 AM, Ani Sinha wrote:

> Igor etc, I just tested this patch using a Windows 2012 R2 image and

> it seems to be working. Any feedbacks on this patch?

>

> On Tue, Aug 11, 2020 at 6:42 PM 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.

>>

>> 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),



From what I understood here, this file is already pretty twisted

and Igor doesn't want more workarounds:

https://www.mail-archive.com/qemu-devel@nongnu.org/msg690564.html



¯\_(ツ)_/¯



>>      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) {

>> --

>> 2.7.4

>>

>