[Qemu-devel] [PATCH v6 3/7] hw/pci-bridge: introduce "hotplug" property

[Laszlo Ersek <lersek@redhat.com>]

In the PCI expander bridge, we will want to disable those features of
pci-bridge that relate to SHPC (standard hotplug controller):

- SHPC bar and underlying MemoryRegion
- interrupt (INTx or MSI)
- effective hotplug callbacks
- other SHPC hooks (initialization, cleanup, migration etc)

Introduce a new feature bit in the PCIBridgeDev.flags field, and turn off
the above if the bit is explicitly cleared.

Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Marcel Apfelbaum <marcel@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---

Notes:
    v6:
    - new in v6 (replaces "hw/pci-bridge: create interrupt-less,
      hotplug-less bridge for PXB" from v5) [Michael]
    - I tested migration-to-file and migration-from-file, with a single PXB
      behind which a virtio-scsi HBA lived
    - No idea how to test the hotplug callbacks. I tried the device_add and
      device_del HMP commands with a virtio-scsi HBA behind the PXB, and the
      monitor reports no error at all; the callbacks don't seem to be
      reached.
    - Retested with windows 2012; it works

 hw/pci-bridge/pci_bridge_dev.c | 90 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 78 insertions(+), 12 deletions(-)

diff --git a/hw/pci-bridge/pci_bridge_dev.c b/hw/pci-bridge/pci_bridge_dev.c
index d697c7b..a0a1ce9 100644
--- a/hw/pci-bridge/pci_bridge_dev.c
+++ b/hw/pci-bridge/pci_bridge_dev.c
@@ -40,10 +40,16 @@ struct PCIBridgeDev {
     MemoryRegion bar;
     uint8_t chassis_nr;
 #define PCI_BRIDGE_DEV_F_MSI_REQ 0
+#define PCI_BRIDGE_DEV_F_HOTPLUG 1
     uint32_t flags;
 };
 typedef struct PCIBridgeDev PCIBridgeDev;
 
+static inline bool hotplug_enabled(const PCIBridgeDev *bridge_dev)
+{
+    return !!(bridge_dev->flags & (1u << PCI_BRIDGE_DEV_F_HOTPLUG));
+}
+
 static int pci_bridge_dev_initfn(PCIDevice *dev)
 {
     PCIBridge *br = PCI_BRIDGE(dev);
@@ -54,16 +60,26 @@ static int pci_bridge_dev_initfn(PCIDevice *dev)
     if (err) {
         goto bridge_error;
     }
-    dev->config[PCI_INTERRUPT_PIN] = 0x1;
-    memory_region_init(&bridge_dev->bar, OBJECT(dev), "shpc-bar", shpc_bar_size(dev));
-    err = shpc_init(dev, &br->sec_bus, &bridge_dev->bar, 0);
-    if (err) {
-        goto shpc_error;
+
+    if (hotplug_enabled(bridge_dev)) {
+        dev->config[PCI_INTERRUPT_PIN] = 0x1;
+        memory_region_init(&bridge_dev->bar, OBJECT(dev), "shpc-bar",
+                           shpc_bar_size(dev));
+        err = shpc_init(dev, &br->sec_bus, &bridge_dev->bar, 0);
+        if (err) {
+            goto shpc_error;
+        }
     }
+
     err = slotid_cap_init(dev, 0, bridge_dev->chassis_nr, 0);
     if (err) {
         goto slotid_error;
     }
+
+    if (!hotplug_enabled(bridge_dev)) {
+        return 0;
+    }
+
     if ((bridge_dev->flags & (1 << PCI_BRIDGE_DEV_F_MSI_REQ)) &&
         msi_supported) {
         err = msi_init(dev, 0, 1, true, true);
@@ -79,7 +95,9 @@ static int pci_bridge_dev_initfn(PCIDevice *dev)
 msi_error:
     slotid_cap_cleanup(dev);
 slotid_error:
-    shpc_cleanup(dev, &bridge_dev->bar);
+    if (hotplug_enabled(bridge_dev)) {
+        shpc_cleanup(dev, &bridge_dev->bar);
+    }
 shpc_error:
     pci_bridge_exitfn(dev);
 bridge_error:
@@ -89,53 +107,101 @@ bridge_error:
 static void pci_bridge_dev_exitfn(PCIDevice *dev)
 {
     PCIBridgeDev *bridge_dev = PCI_BRIDGE_DEV(dev);
+
     if (msi_present(dev)) {
         msi_uninit(dev);
     }
     slotid_cap_cleanup(dev);
-    shpc_cleanup(dev, &bridge_dev->bar);
+    if (hotplug_enabled(bridge_dev)) {
+        shpc_cleanup(dev, &bridge_dev->bar);
+    }
     pci_bridge_exitfn(dev);
 }
 
 static void pci_bridge_dev_instance_finalize(Object *obj)
 {
+    /* this function is idempotent and handles (PCIDevice.shpc == NULL) */
     shpc_free(PCI_DEVICE(obj));
 }
 
 static void pci_bridge_dev_write_config(PCIDevice *d,
                                         uint32_t address, uint32_t val, int len)
 {
+    PCIBridgeDev *bridge_dev = PCI_BRIDGE_DEV(d);
+
     pci_bridge_write_config(d, address, val, len);
     if (msi_present(d)) {
         msi_write_config(d, address, val, len);
     }
-    shpc_cap_write_config(d, address, val, len);
+    if (hotplug_enabled(bridge_dev)) {
+        shpc_cap_write_config(d, address, val, len);
+    }
 }
 
 static void qdev_pci_bridge_dev_reset(DeviceState *qdev)
 {
     PCIDevice *dev = PCI_DEVICE(qdev);
+    PCIBridgeDev *bridge_dev = PCI_BRIDGE_DEV(dev);
 
     pci_bridge_reset(qdev);
-    shpc_reset(dev);
+    if (hotplug_enabled(bridge_dev)) {
+        shpc_reset(dev);
+    }
 }
 
 static Property pci_bridge_dev_properties[] = {
                     /* Note: 0 is not a legal chassis number. */
     DEFINE_PROP_UINT8("chassis_nr", PCIBridgeDev, chassis_nr, 0),
     DEFINE_PROP_BIT("msi", PCIBridgeDev, flags, PCI_BRIDGE_DEV_F_MSI_REQ, true),
+    DEFINE_PROP_BIT("hotplug", PCIBridgeDev, flags, PCI_BRIDGE_DEV_F_HOTPLUG,
+                    true),
     DEFINE_PROP_END_OF_LIST(),
 };
 
+static bool pci_bridge_dev_shpc_exists(void *opaque, int version_id)
+{
+    PCIDevice *dev = opaque;
+    PCIBridgeDev *bridge_dev = PCI_BRIDGE_DEV(dev);
+
+    return hotplug_enabled(bridge_dev);
+}
+
 static const VMStateDescription pci_bridge_dev_vmstate = {
     .name = "pci_bridge",
     .fields = (VMStateField[]) {
         VMSTATE_PCI_DEVICE(parent_obj, PCIBridge),
-        SHPC_VMSTATE(shpc, PCIDevice, NULL),
+        SHPC_VMSTATE(shpc, PCIDevice, pci_bridge_dev_shpc_exists),
         VMSTATE_END_OF_LIST()
     }
 };
 
+static void pci_bridge_dev_hotplug_cb(HotplugHandler *hotplug_dev,
+                                      DeviceState *dev, Error **errp)
+{
+    PCIBridgeDev *bridge_dev = PCI_BRIDGE_DEV(hotplug_dev);
+
+    if (!hotplug_enabled(bridge_dev)) {
+        error_setg(errp, "standard hotplug controller has been disabled for "
+                   "this %s", TYPE_PCI_BRIDGE_DEV);
+        return;
+    }
+    shpc_device_hotplug_cb(hotplug_dev, dev, errp);
+}
+
+static void pci_bridge_dev_hot_unplug_request_cb(HotplugHandler *hotplug_dev,
+                                                 DeviceState *dev,
+                                                 Error **errp)
+{
+    PCIBridgeDev *bridge_dev = PCI_BRIDGE_DEV(hotplug_dev);
+
+    if (!hotplug_enabled(bridge_dev)) {
+        error_setg(errp, "standard hotplug controller has been disabled for "
+                   "this %s", TYPE_PCI_BRIDGE_DEV);
+        return;
+    }
+    shpc_device_hot_unplug_request_cb(hotplug_dev, dev, errp);
+}
+
 static void pci_bridge_dev_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
@@ -154,8 +220,8 @@ static void pci_bridge_dev_class_init(ObjectClass *klass, void *data)
     dc->props = pci_bridge_dev_properties;
     dc->vmsd = &pci_bridge_dev_vmstate;
     set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories);
-    hc->plug = shpc_device_hotplug_cb;
-    hc->unplug_request = shpc_device_hot_unplug_request_cb;
+    hc->plug = pci_bridge_dev_hotplug_cb;
+    hc->unplug_request = pci_bridge_dev_hot_unplug_request_cb;
 }
 
 static const TypeInfo pci_bridge_dev_info = {
-- 
1.8.3.1