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

[Ani Sinha]

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 | 23 ++++++++++++++++++-----
 2 files changed, 21 insertions(+), 5 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..1881009 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)
@@ -337,14 +341,18 @@ 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);
+    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));
 
@@ -361,6 +369,9 @@ 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 +430,7 @@ 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 +450,8 @@ 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 +1830,8 @@ 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