pcie: implement slot power control for pcie root ports

With this patch hot-plugged pci devices will only be visible to the
guest if the guests hotplug driver has enabled slot power.

This should fix the hot-plug race which one can hit when hot-plugging
a pci device at boot, while the guest is in the middle of the pci bus
scan.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-Id: <20211111130859.1171890-3-kraxel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/pci/pcie.c

@@ -366,6 +366,29 @@ static void hotplug_event_clear(PCIDevice *dev)
     }
 }
 
+static void pcie_set_power_device(PCIBus *bus, PCIDevice *dev, void *opaque)
+{
+    bool *power = opaque;
+
+    pci_set_power(dev, *power);
+}
+
+static void pcie_cap_update_power(PCIDevice *hotplug_dev)
+{
+    uint8_t *exp_cap = hotplug_dev->config + hotplug_dev->exp.exp_cap;
+    PCIBus *sec_bus = pci_bridge_get_sec_bus(PCI_BRIDGE(hotplug_dev));
+    uint32_t sltcap = pci_get_long(exp_cap + PCI_EXP_SLTCAP);
+    uint16_t sltctl = pci_get_word(exp_cap + PCI_EXP_SLTCTL);
+    bool power = true;
+
+    if (sltcap & PCI_EXP_SLTCAP_PCP) {
+        power = (sltctl & PCI_EXP_SLTCTL_PCC) == PCI_EXP_SLTCTL_PWR_ON;
+    }
+
+    pci_for_each_device(sec_bus, pci_bus_num(sec_bus),
+                        pcie_set_power_device, &power);
+}
+
 /*
  * A PCI Express Hot-Plug Event has occurred, so update slot status register
  * and notify OS of the event if necessary.
@@ -434,6 +457,7 @@ void pcie_cap_slot_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
             pci_word_test_and_set_mask(exp_cap + PCI_EXP_LNKSTA,
                                        PCI_EXP_LNKSTA_DLLLA);
         }
+        pcie_cap_update_power(hotplug_pdev);
         return;
     }
 
@@ -451,6 +475,7 @@ void pcie_cap_slot_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
         }
         pcie_cap_slot_event(hotplug_pdev,
                             PCI_EXP_HP_EV_PDC | PCI_EXP_HP_EV_ABP);
+        pcie_cap_update_power(hotplug_pdev);
     }
 }
 
@@ -625,6 +650,7 @@ void pcie_cap_slot_reset(PCIDevice *dev)
                                  PCI_EXP_SLTSTA_PDC |
                                  PCI_EXP_SLTSTA_ABP);
 
+    pcie_cap_update_power(dev);
     hotplug_event_update_event_status(dev);
 }
 
@@ -705,6 +731,7 @@ void pcie_cap_slot_write_config(PCIDevice *dev,
         pci_word_test_and_set_mask(exp_cap + PCI_EXP_SLTSTA,
                                        PCI_EXP_SLTSTA_PDC);
     }
+    pcie_cap_update_power(dev);
 
     hotplug_event_notify(dev);
 
@@ -731,6 +758,7 @@ int pcie_cap_slot_post_load(void *opaque, int version_id)
 {
     PCIDevice *dev = opaque;
     hotplug_event_update_event_status(dev);
+    pcie_cap_update_power(dev);
     return 0;
 }