qemu: simplify PCI configfd handling in monitor

This is also a bug fix - on the error path, qemu_hotplug would
leave the configfd file leaked into qemu.  At least the next
attempt to hotplug a PCI device would reuse the same fdname,
and when the qemu getfd monitor command gets a new fd by the
same name as an earlier one, it closes the earlier one, so there
is no risk of qemu running out of fds.

* src/qemu/qemu_monitor.h (qemuMonitorAddDeviceWithFd): New
prototype.
* src/qemu/qemu_monitor.c (qemuMonitorAddDevice): Move guts...
(qemuMonitorAddDeviceWithFd): ...to new function, and add support
for fd passing.
* src/qemu/qemu_hotplug.c (qemuDomainAttachHostPciDevice): Use it
to simplify code.
Suggested by Daniel P. Berrange.

src/qemu/qemu_hotplug.c

@@ -820,14 +820,6 @@ int qemuDomainAttachHostPciDevice(struct qemud_driver *driver,
                     virReportOOMError();
                     goto error;
                 }
-
-                qemuDomainObjEnterMonitorWithDriver(driver, vm);
-                if (qemuMonitorSendFileHandle(priv->mon, configfd_name,
-                                              configfd) < 0) {
-                    qemuDomainObjExitMonitorWithDriver(driver, vm);
-                    goto error;
-                }
-                qemuDomainObjExitMonitorWithDriver(driver, vm);
             }
         }
 
@@ -842,7 +834,8 @@ int qemuDomainAttachHostPciDevice(struct qemud_driver *driver,
             goto error;
 
         qemuDomainObjEnterMonitorWithDriver(driver, vm);
-        ret = qemuMonitorAddDevice(priv->mon, devstr);
+        ret = qemuMonitorAddDeviceWithFd(priv->mon, devstr,
+                                         configfd, configfd_name);
         qemuDomainObjExitMonitorWithDriver(driver, vm);
     } else {
         virDomainDevicePCIAddress guestAddr;

src/qemu/qemu_monitor.c

@@ -2030,10 +2030,13 @@ int qemuMonitorDelDevice(qemuMonitorPtr mon,
 }
 
 
-int qemuMonitorAddDevice(qemuMonitorPtr mon,
-                         const char *devicestr)
+int qemuMonitorAddDeviceWithFd(qemuMonitorPtr mon,
+                               const char *devicestr,
+                               int fd,
+                               const char *fdname)
 {
-    VIR_DEBUG("mon=%p device=%s", mon, devicestr);
+    VIR_DEBUG("mon=%p device=%s fd=%d fdname=%s", mon, devicestr, fd,
+              NULLSTR(fdname));
     int ret;
 
     if (!mon) {
@@ -2042,13 +2045,28 @@ int qemuMonitorAddDevice(qemuMonitorPtr mon,
         return -1;
     }
 
+    if (fd >= 0 && qemuMonitorSendFileHandle(mon, fdname, fd) < 0)
+        return -1;
+
     if (mon->json)
         ret = qemuMonitorJSONAddDevice(mon, devicestr);
     else
         ret = qemuMonitorTextAddDevice(mon, devicestr);
+
+    if (ret < 0 && fd >= 0) {
+        if (qemuMonitorCloseFileHandle(mon, fdname) < 0)
+            VIR_WARN("failed to close device handle '%s'", fdname);
+    }
+
     return ret;
 }
 
+int qemuMonitorAddDevice(qemuMonitorPtr mon,
+                         const char *devicestr)
+{
+    return qemuMonitorAddDeviceWithFd(mon, devicestr, -1, NULL);
+}
+
 int qemuMonitorAddDrive(qemuMonitorPtr mon,
                         const char *drivestr)
 {

src/qemu/qemu_monitor.h

@@ -390,6 +390,11 @@ int qemuMonitorGetAllPCIAddresses(qemuMonitorPtr mon,
 int qemuMonitorAddDevice(qemuMonitorPtr mon,
                          const char *devicestr);
 
+int qemuMonitorAddDeviceWithFd(qemuMonitorPtr mon,
+                               const char *devicestr,
+                               int fd,
+                               const char *fdname);
+
 int qemuMonitorDelDevice(qemuMonitorPtr mon,
                          const char *devalias);