pci: Simpler implementation of primary PCI bus

Currently pci_find_primary_bus() searches the list of root buses for one
with domain 0.  But since host buses are always registered with domain 0,
this just amounts to finding the only PCI host bus.  The only remaining
users of pci_find_primary_bus() are in pci-hotplug-old.c, which implements
the old style pci_add/pci_del commands.

Therefore, this patch redefines pci_find_primary_bus() to find the only
PCI root bus, returning an error if there are multiple roots.  The callers
in pci-hotplug-old.c are updated correspondingly, to produce sensible
error messages.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

2 files changed, 26 insertions, 9 deletions

diff --git a/hw/pci/pci-hotplug-old.c b/hw/pci/pci-hotplug-old.c
index 807260cce9..8077289756 100644
--- a/hw/pci/pci-hotplug-old.c
+++ b/hw/pci/pci-hotplug-old.c
@@ -62,10 +62,17 @@ static PCIDevice *qemu_pci_hot_add_nic(Monitor *mon,
 {
     Error *local_err = NULL;
     QemuOpts *opts;
+    PCIBus *root = pci_find_primary_bus();
     PCIBus *bus;
     int ret, devfn;
 
-    bus = pci_get_bus_devfn(&devfn, pci_find_primary_bus(), devaddr);
+    if (!root) {
+        monitor_printf(mon, "no primary PCI bus (if there are multiple"
+                       " PCI roots, you must use device_add instead)");
+        return NULL;
+    }
+
+    bus = pci_get_bus_devfn(&devfn, root, devaddr);
     if (!bus) {
         monitor_printf(mon, "Invalid PCI device address %s\n", devaddr);
         return NULL;
@@ -92,8 +99,7 @@ static PCIDevice *qemu_pci_hot_add_nic(Monitor *mon,
         monitor_printf(mon, "Parameter addr not supported\n");
         return NULL;
     }
-    return pci_nic_init(&nd_table[ret], pci_find_primary_bus(),
-                        "rtl8139", devaddr);
+    return pci_nic_init(&nd_table[ret], root, "rtl8139", devaddr);
 }
 
 static int scsi_hot_add(Monitor *mon, DeviceState *adapter,
@@ -144,7 +150,8 @@ int pci_drive_hot_add(Monitor *mon, const QDict *qdict, DriveInfo *dinfo)
     switch (dinfo->type) {
     case IF_SCSI:
         if (!root) {
-            monitor_printf(mon, "no primary PCI bus\n");
+            monitor_printf(mon, "no primary PCI bus (if there are multiple"
+                           " PCI roots, you must use device_add instead)");
             goto err;
         }
         if (pci_read_devaddr(mon, pci_addr, &pci_bus, &slot)) {
@@ -177,6 +184,7 @@ static PCIDevice *qemu_pci_hot_add_storage(Monitor *mon,
     DriveInfo *dinfo = NULL;
     int type = -1;
     char buf[128];
+    PCIBus *root = pci_find_primary_bus();
     PCIBus *bus;
     int devfn;
 
@@ -206,7 +214,12 @@ static PCIDevice *qemu_pci_hot_add_storage(Monitor *mon,
         dinfo = NULL;
     }
 
-    bus = pci_get_bus_devfn(&devfn, pci_find_primary_bus(), devaddr);
+    if (!root) {
+        monitor_printf(mon, "no primary PCI bus (if there are multiple"
+                       " PCI roots, you must use device_add instead)");
+        return NULL;
+    }
+    bus = pci_get_bus_devfn(&devfn, root, devaddr);
     if (!bus) {
         monitor_printf(mon, "Invalid PCI device address %s\n", devaddr);
         return NULL;
@@ -293,7 +306,8 @@ static int pci_device_hot_remove(Monitor *mon, const char *pci_addr)
     Error *local_err = NULL;
 
     if (!root) {
-        monitor_printf(mon, "no primary PCI bus\n");
+        monitor_printf(mon, "no primary PCI bus (if there are multiple"
+                       " PCI roots, you must use device_del instead)");
         return -1;
     }
 
diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 2f2db0f8df..e0995aa950 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -249,15 +249,18 @@ static void pci_host_bus_register(int domain, PCIBus *bus)
 
 PCIBus *pci_find_primary_bus(void)
 {
+    PCIBus *primary_bus = NULL;
     struct PCIHostBus *host;
 
     QLIST_FOREACH(host, &host_buses, next) {
-        if (host->domain == 0) {
-            return host->bus;
+        if (primary_bus) {
+            /* We have multiple root buses, refuse to select a primary */
+            return NULL;
         }
+        primary_bus = host->bus;
     }
 
-    return NULL;
+    return primary_bus;
 }
 
 PCIBus *pci_device_root_bus(const PCIDevice *d)