conf: pay attention to bus minSlot/maxSlot when autoassigning PCI addresses

The function that auto-assigns PCI addresses was written with the
hardcoded assumptions that any PCI bus would have slots available
starting at 1 and ending at 31. This isn't true for many types of
controllers (some have a single slot/port at 0, some have slots/ports
from 0 to 31). This patch updates that function to remove the
hardcoded assumptions. It will properly find/assign addresses for
devices that can only connect to pcie-(root|downstream)-port (which
have minSlot/maxSlot of 0/0) or a pcie-switch-upstream-port (0/31).

It still will not auto-create a new bus of the proper kind for these
connections when one doesn't exist, that task is for another day.

src/conf/domain_addr.c

@@ -471,55 +471,66 @@ virDomainPCIAddressGetNextSlot(virDomainPCIAddressSetPtr addrs,
                                virDomainPCIConnectFlags flags)
 {
     /* default to starting the search for a free slot from
-     * 0000:00:00.0
+     * the first slot of domain 0 bus 0...
      */
     virDevicePCIAddress a = { 0, 0, 0, 0, false };
     char *addrStr = NULL;
 
-    /* except if this search is for the exact same type of device as
-     * last time, continue the search from the previous match
-     */
-    if (flags == addrs->lastFlags)
-        a = addrs->lastaddr;
-
     if (addrs->nbuses == 0) {
         virReportError(VIR_ERR_XML_ERROR, "%s", _("No PCI buses available"));
         goto error;
     }
 
-    /* Start the search at the last used bus and slot */
-    for (a.slot++; a.bus < addrs->nbuses; a.bus++) {
+    /* ...unless this search is for the exact same type of device as
+     * last time, then continue the search from the next slot after
+     * the previous match (the "next slot" may possibly be the first
+     * slot of the next bus).
+     */
+    if (flags == addrs->lastFlags) {
+        a = addrs->lastaddr;
+        if (++a.slot > addrs->buses[a.bus].maxSlot &&
+            ++a.bus < addrs->nbuses)
+            a.slot = addrs->buses[a.bus].minSlot;
+    } else {
+        a.slot = addrs->buses[0].minSlot;
+    }
+
+    while (a.bus < addrs->nbuses) {
+        VIR_FREE(addrStr);
         if (!(addrStr = virDomainPCIAddressAsString(&a)))
             goto error;
         if (!virDomainPCIAddressFlagsCompatible(&a, addrStr,
                                                 addrs->buses[a.bus].flags,
                                                 flags, false, false)) {
-            VIR_FREE(addrStr);
             VIR_DEBUG("PCI bus %.4x:%.2x is not compatible with the device",
                       a.domain, a.bus);
-            continue;
-        }
-        for (; a.slot <= VIR_PCI_ADDRESS_SLOT_LAST; a.slot++) {
-            if (!virDomainPCIAddressSlotInUse(addrs, &a))
-                goto success;
+        } else {
+            while (a.slot <= addrs->buses[a.bus].maxSlot) {
+                if (!virDomainPCIAddressSlotInUse(addrs, &a))
+                    goto success;
 
-            VIR_DEBUG("PCI slot %.4x:%.2x:%.2x already in use",
-                      a.domain, a.bus, a.slot);
+                VIR_DEBUG("PCI slot %.4x:%.2x:%.2x already in use",
+                          a.domain, a.bus, a.slot);
+                a.slot++;
+            }
         }
-        a.slot = 1;
-        VIR_FREE(addrStr);
+        if (++a.bus < addrs->nbuses)
+            a.slot = addrs->buses[a.bus].minSlot;
     }
 
     /* There were no free slots after the last used one */
     if (addrs->dryRun) {
-        /* a is already set to the first new bus and slot 1 */
+        /* a is already set to the first new bus */
         if (virDomainPCIAddressSetGrow(addrs, &a, flags) < 0)
             goto error;
+        /* this device will use the first slot of the new bus */
+        a.slot = addrs->buses[a.bus].minSlot;
         goto success;
     } else if (flags == addrs->lastFlags) {
         /* Check the buses from 0 up to the last used one */
         for (a.bus = 0; a.bus <= addrs->lastaddr.bus; a.bus++) {
-            addrStr = NULL;
+            a.slot = addrs->buses[a.bus].minSlot;
+            VIR_FREE(addrStr);
             if (!(addrStr = virDomainPCIAddressAsString(&a)))
                 goto error;
             if (!virDomainPCIAddressFlagsCompatible(&a, addrStr,
@@ -527,14 +538,15 @@ virDomainPCIAddressGetNextSlot(virDomainPCIAddressSetPtr addrs,
                                                     flags, false, false)) {
                 VIR_DEBUG("PCI bus %.4x:%.2x is not compatible with the device",
                           a.domain, a.bus);
-                continue;
-            }
-            for (a.slot = 1; a.slot <= VIR_PCI_ADDRESS_SLOT_LAST; a.slot++) {
-                if (!virDomainPCIAddressSlotInUse(addrs, &a))
-                    goto success;
-
-                VIR_DEBUG("PCI slot %.4x:%.2x:%.2x already in use",
-                          a.domain, a.bus, a.slot);
+            } else {
+                while (a.slot <= addrs->buses[a.bus].maxSlot) {
+                    if (!virDomainPCIAddressSlotInUse(addrs, &a))
+                        goto success;
+
+                    VIR_DEBUG("PCI slot %.4x:%.2x:%.2x already in use",
+                              a.domain, a.bus, a.slot);
+                    a.slot++;
+                }
             }
         }
     }