Add support for file descriptor sets by converting some of the 
command line parameters to use /dev/fdset/%d if -add-fd is found
to be supported by QEMU. For those devices libvirt now open()s
the device to obtain the file descriptor and 'transfers' the 
fd using virCommand.

For the following fragments of domain XML


    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/var/lib/libvirt/images/fc14-x86_64.img'/>
      <target dev='hda' bus='ide'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>

   <serial type='dev'>
      <source path='/dev/ttyS0'/>
      <target port='0'/>
    </serial>
    <serial type='pipe'>
      <source path='/tmp/testpipe'/>
      <target port='1'/>
    </serial>

libvirt now creates the following parts for the QEMU command line:

old: -drive file=/var/lib/libvirt/images/fc14-x86_64.img,if=none,id=drive-ide0-0-0,format=raw
new: -add-fd set=1,fd=23,opaque=RDONLY:/var/lib/libvirt/images/fc14-x86_64.img
     -add-fd set=1,fd=24,opaque=RDWR:/var/lib/libvirt/images/fc14-x86_64.img
     -drive file=/dev/fdset/1,if=none,id=drive-ide0-0-0,format=raw

old: -chardev tty,id=charserial0,path=/dev/ttyS0
new: -add-fd set=1,fd=30,opaque=/dev/ttyS0
     -chardev tty,id=charserial0,path=/dev/fdset/1

old: -chardev pipe,id=charserial1,path=/tmp/testpipe
new: -add-fd set=2,fd=32,opaque=/tmp/testpipe
     -chardev pipe,id=charserial1,path=/dev/fdset/2

Test cases are part of this patch now.

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>

---
v4->v5:
   - removed one test case testing for 'old' command line

v3->v4:
   - Adapt to changes in patch 1
   - better handling of error case on the hotplug code

v2->v3:
   - Use an unsigned int for remembering the next-to-use fdset

v1->v2:
   - Addressed many of Eric's comment; many changes, though
   - virBitmap holds used file descriptor sets; it's attached to
     QEMU private domain structure
   - persisting and parsing the fdset in the virDomainDeviceInfo XML
   - rebuilding the fdset bitmap upon libvirt start and after parsing
     the virDomainDeviceInfo XML

---
 src/qemu/qemu_command.c                         |  244 +++++++++++++++++++-----
 src/qemu/qemu_command.h                         |   14 +
 src/qemu/qemu_driver.c                          |    5 
 src/qemu/qemu_driver.h                          |    4 
 src/qemu/qemu_hotplug.c                         |   15 +
 src/qemu/qemu_process.c                         |    6 
 tests/qemuxml2argvdata/qemuxml2argv-add-fd.args |   23 ++
 tests/qemuxml2argvdata/qemuxml2argv-add-fd.xml  |   36 +++
 tests/qemuxml2argvtest.c                        |   11 -
 tests/qemuxmlnstest.c                           |    8 
 10 files changed, 309 insertions(+), 57 deletions(-)

Index: libvirt/src/qemu/qemu_command.c
===================================================================
--- libvirt.orig/src/qemu/qemu_command.c
+++ libvirt/src/qemu/qemu_command.c
@@ -46,6 +46,7 @@
 #include "base64.h"
 #include "device_conf.h"
 #include "virstoragefile.h"
+#include "qemu_driver.h"
 
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -133,6 +134,70 @@ VIR_ENUM_IMPL(qemuDomainFSDriver, VIR_DO
 
 
 /**
+ * qemuCommandPrintFDSet:
+ * @fdset: the number of the file descriptor set to which @fd belongs
+ * @fd: fd that will be assigned to QEMU
+ * @open_flags: the flags used for opening the fd; of interest are only
+ *               O_RDONLY, O_WRONLY, O_RDWR
+ * @name: optional name of the file
+ *
+ * Write the parameters for the QEMU -add-fd command line option
+ * for the given file descriptor and return the string.
+ * This function for example returns "set=10,fd=20,opaque=RDWR:/foo/bar".
+ */
+static char *
+qemuCommandPrintFDSet(int fdset, int fd, int open_flags, const char *name)
+{
+    const char *mode = "";
+    virBuffer buf = VIR_BUFFER_INITIALIZER;
+
+    if (name) {
+        switch ((open_flags & O_ACCMODE)) {
+        case O_RDONLY:
+            mode = "RDONLY:";
+            break;
+        case O_WRONLY:
+            mode = "WRONLY:";
+            break;
+        case O_RDWR:
+            mode = "RDWR:";
+            break;
+        }
+    }
+
+    virBufferAsprintf(&buf, "set=%d,fd=%d%s%s", fdset, fd,
+                      (name) ? ",opaque=" : "",
+                      mode);
+    if (name)
+        virBufferEscape(&buf, ',', ",", "%s", name);
+
+    if (virBufferError(&buf)) {
+        virReportOOMError();
+        virBufferFreeAndReset(&buf);
+        return NULL;
+    }
+
+    return virBufferContentAndReset(&buf);
+}
+
+/**
+ * qemuCommandPrintDevSet:
+ * @buf: buffer to write the file descriptor set string
+ * @fdset: the file descriptor set
+ *
+ * Get the parameters for the QEMU path= parameter where a file
+ * descriptor is accessed via a file descriptor set, for example
+ * /dev/fdset/10. The file descriptor must previously have been
+ * 'transferred' in a virCommandTransfer() call.
+ */
+static void
+qemuCommandPrintDevSet(virBufferPtr buf, int fdset)
+{
+    virBufferAsprintf(buf, "/dev/fdset/%d", fdset);
+}
+
+
+/**
  * qemuPhysIfaceConnect:
  * @def: the definition of the VM (needed by 802.1Qbh and audit)
  * @driver: pointer to the driver instance
@@ -2229,11 +2294,70 @@ no_memory:
     goto cleanup;
 }
 
+static int
+qemuCreatePathForFilePath(virQEMUDriverPtr driver, virBufferPtr buf,
+                          const char *prefix, const char *path,
+                          const int *open_flags,
+                          virCommandPtr cmd, virFdSetPtr fdset,
+                          const virDomainDeviceInfoPtr info,
+                          virQEMUCapsPtr qemuCaps)
+{
+    char *fdsetstr = NULL;
+    int i;
+
+    virBufferAdd(buf, prefix, -1);
+    /*
+     * cmd == NULL hints at hotplugging; use old way of doing things
+     * fdset == NULL hints at a call path where we should not open files
+     *               In this case we fall back to the old command line
+     *               (at least for now)
+     */
+    if (!cmd || !fdset || !virQEMUCapsGet(qemuCaps, QEMU_CAPS_ADD_FD)) {
+        virBufferEscape(buf, ',', ",", "%s", path);
+    } else {
+        unsigned int fdsetnum;
+
+        if (virFdSetNextSet(fdset, info->alias, &fdsetnum) < 0)
+            goto error;
+
+        qemuCommandPrintDevSet(buf, fdsetnum);
+
+        i = 0;
+        while (open_flags[i] != -1) {
+            int fd = qemuOpenFile(driver, path, open_flags[i], NULL, NULL);
+            if (fd < 0) {
+                virReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("Could not open %s"), path);
+                goto error;
+            }
+            virCommandTransferFD(cmd, fd);
+
+            fdsetstr = qemuCommandPrintFDSet(fdsetnum, fd, open_flags[i],
+                                             path);
+            if (!fdsetstr)
+                goto error;
+            virCommandAddArgList(cmd, "-add-fd", fdsetstr, NULL);
+            VIR_FREE(fdsetstr);
+
+            i++;
+        }
+    }
+
+    return 0;
+
+error:
+    virFdSetRemoveAlias(fdset, info->alias);
+    return -1;
+}
+
 char *
 qemuBuildDriveStr(virConnectPtr conn ATTRIBUTE_UNUSED,
                   virDomainDiskDefPtr disk,
                   bool bootable,
-                  virQEMUCapsPtr qemuCaps)
+                  virQEMUCapsPtr qemuCaps,
+                  virCommandPtr cmd,
+                  virQEMUDriverPtr driver,
+                  virFdSetPtr fdset)
 {
     virBuffer opt = VIR_BUFFER_INITIALIZER;
     const char *bus = virDomainDiskQEMUBusTypeToString(disk->bus);
@@ -2395,7 +2519,13 @@ qemuBuildDriveStr(virConnectPtr conn ATT
                                  "block type disk"));
                 goto error;
             }
-            virBufferEscape(&opt, ',', ",", "file=%s,", disk->src);
+            if (qemuCreatePathForFilePath(driver, &opt,
+                                          "file=", disk->src,
+                                          (int[]){O_RDONLY, O_RDWR, -1},
+                                          cmd, fdset, &disk->info,
+                                          qemuCaps) < 0)
+                goto error;
+            virBufferAddChar(&opt, ',');
         }
     }
     if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE))
@@ -2892,7 +3022,10 @@ error:
 
 
 char *qemuBuildFSStr(virDomainFSDefPtr fs,
-                     virQEMUCapsPtr qemuCaps ATTRIBUTE_UNUSED)
+                     virQEMUCapsPtr qemuCaps ATTRIBUTE_UNUSED,
+                     virCommandPtr cmd,
+                     virQEMUDriverPtr qemu_driver,
+                     virFdSetPtr fdset)
 {
     virBuffer opt = VIR_BUFFER_INITIALIZER;
     const char *driver = qemuDomainFSDriverTypeToString(fs->fsdriver);
@@ -2941,7 +3074,10 @@ char *qemuBuildFSStr(virDomainFSDefPtr f
     }
 
     virBufferAsprintf(&opt, ",id=%s%s", QEMU_FSDEV_HOST_PREFIX, fs->info.alias);
-    virBufferAsprintf(&opt, ",path=%s", fs->src);
+    if (qemuCreatePathForFilePath(qemu_driver, &opt,
+                                  ",path=", fs->src, (int[]){O_RDWR, -1},
+                                  cmd, fdset, &fs->info, qemuCaps) < 0)
+        goto error;
 
     if (fs->readonly) {
         if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_FSDEV_READONLY)) {
@@ -3894,12 +4030,14 @@ qemuBuildUSBHostdevUsbDevStr(virDomainHo
 }
 
 
-
 /* This function outputs a -chardev command line option which describes only the
  * host side of the character device */
 static char *
 qemuBuildChrChardevStr(virDomainChrSourceDefPtr dev, const char *alias,
-                       virQEMUCapsPtr qemuCaps)
+                       virQEMUCapsPtr qemuCaps, virCommandPtr cmd,
+                       virQEMUDriverPtr driver,
+                       virFdSetPtr fdset,
+                       const virDomainDeviceInfoPtr info)
 {
     virBuffer buf = VIR_BUFFER_INITIALIZER;
     bool telnet;
@@ -3918,19 +4056,32 @@ qemuBuildChrChardevStr(virDomainChrSourc
         break;
 
     case VIR_DOMAIN_CHR_TYPE_DEV:
-        virBufferAsprintf(&buf, "%s,id=char%s,path=%s",
+        virBufferAsprintf(&buf, "%s,id=char%s",
                           STRPREFIX(alias, "parallel") ? "parport" : "tty",
-                          alias, dev->data.file.path);
+                          alias);
+        if (qemuCreatePathForFilePath(driver, &buf,
+                                      ",path=", dev->data.file.path,
+                                      (int[]){O_RDWR, -1}, cmd, fdset,
+                                      info, qemuCaps) < 0)
+            goto error;
         break;
 
     case VIR_DOMAIN_CHR_TYPE_FILE:
-        virBufferAsprintf(&buf, "file,id=char%s,path=%s", alias,
-                          dev->data.file.path);
+        virBufferAsprintf(&buf, "file,id=char%s", alias);
+        if (qemuCreatePathForFilePath(driver, &buf,
+                                      ",path=", dev->data.file.path,
+                                      (int[]){O_RDWR, -1}, cmd, fdset,
+                                      info, qemuCaps) < 0)
+            goto error;
         break;
 
     case VIR_DOMAIN_CHR_TYPE_PIPE:
-        virBufferAsprintf(&buf, "pipe,id=char%s,path=%s", alias,
-                          dev->data.file.path);
+        virBufferAsprintf(&buf, "pipe,id=char%s",alias);
+        if (qemuCreatePathForFilePath(driver, &buf,
+                                      ",path=", dev->data.file.path,
+                                      (int[]){O_RDWR, -1}, cmd,
+                                      fdset, info, qemuCaps) < 0)
+            goto error;
         break;
 
     case VIR_DOMAIN_CHR_TYPE_STDIO:
@@ -5072,7 +5223,8 @@ qemuBuildCommandLine(virConnectPtr conn,
                      const char *migrateFrom,
                      int migrateFd,
                      virDomainSnapshotObjPtr snapshot,
-                     enum virNetDevVPortProfileOp vmop)
+                     enum virNetDevVPortProfileOp vmop,
+                     virFdSetPtr fdset)
 {
     int i, j;
     int disableKQEMU = 0;
@@ -5367,11 +5519,11 @@ qemuBuildCommandLine(virConnectPtr conn,
         /* Use -chardev if it's available */
         if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_CHARDEV)) {
 
-            virCommandAddArg(cmd, "-chardev");
             if (!(chrdev = qemuBuildChrChardevStr(monitor_chr, "monitor",
-                                                  qemuCaps)))
+                                                  qemuCaps, cmd, driver, fdset,
+                                                  NULL)))
                 goto error;
-            virCommandAddArg(cmd, chrdev);
+            virCommandAddArgList(cmd, "-chardev", chrdev, NULL);
             VIR_FREE(chrdev);
 
             virCommandAddArg(cmd, "-mon");
@@ -5818,8 +5970,6 @@ qemuBuildCommandLine(virConnectPtr conn,
                 break;
             }
 
-            virCommandAddArg(cmd, "-drive");
-
             /* Unfortunately it is not possible to use
                -device for floppies, or Xen paravirt
                devices. Fortunately, those don't need
@@ -5835,12 +5985,12 @@ qemuBuildCommandLine(virConnectPtr conn,
             }
             optstr = qemuBuildDriveStr(conn, disk,
                                        emitBootindex ? false : !!bootindex,
-                                       qemuCaps);
+                                       qemuCaps, cmd, driver, fdset);
             if (deviceFlagMasked)
                 virQEMUCapsSet(qemuCaps, QEMU_CAPS_DEVICE);
             if (!optstr)
                 goto error;
-            virCommandAddArg(cmd, optstr);
+            virCommandAddArgList(cmd, "-drive", optstr, NULL);
             VIR_FREE(optstr);
 
             if (!emitBootindex)
@@ -6016,7 +6166,7 @@ qemuBuildCommandLine(virConnectPtr conn,
             virDomainFSDefPtr fs = def->fss[i];
 
             virCommandAddArg(cmd, "-fsdev");
-            if (!(optstr = qemuBuildFSStr(fs, qemuCaps)))
+            if (!(optstr = qemuBuildFSStr(fs, qemuCaps, cmd, driver, fdset)))
                 goto error;
             virCommandAddArg(cmd, optstr);
             VIR_FREE(optstr);
@@ -6297,14 +6447,14 @@ qemuBuildCommandLine(virConnectPtr conn,
                 goto error;
             }
 
-            virCommandAddArg(cmd, "-chardev");
             if (!(devstr = qemuBuildChrChardevStr(&smartcard->data.passthru,
                                                   smartcard->info.alias,
-                                                  qemuCaps))) {
+                                                  qemuCaps, cmd, driver, fdset,
+                                                  &smartcard->info))) {
                 virBufferFreeAndReset(&opt);
                 goto error;
             }
-            virCommandAddArg(cmd, devstr);
+            virCommandAddArgList(cmd, "-chardev", devstr, NULL);
             VIR_FREE(devstr);
 
             virBufferAsprintf(&opt, "ccid-card-passthru,chardev=char%s",
@@ -6335,12 +6485,13 @@ qemuBuildCommandLine(virConnectPtr conn,
             /* Use -chardev with -device if they are available */
             if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_CHARDEV) &&
                 virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE)) {
-                virCommandAddArg(cmd, "-chardev");
                 if (!(devstr = qemuBuildChrChardevStr(&serial->source,
                                                       serial->info.alias,
-                                                      qemuCaps)))
+                                                      qemuCaps, cmd, driver,
+                                                      fdset,
+                                                      &serial->info)))
                     goto error;
-                virCommandAddArg(cmd, devstr);
+                virCommandAddArgList(cmd, "-chardev", devstr, NULL);
                 VIR_FREE(devstr);
 
                 virCommandAddArg(cmd, "-device");
@@ -6372,12 +6523,13 @@ qemuBuildCommandLine(virConnectPtr conn,
             /* Use -chardev with -device if they are available */
             if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_CHARDEV) &&
                 virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE)) {
-                virCommandAddArg(cmd, "-chardev");
                 if (!(devstr = qemuBuildChrChardevStr(&parallel->source,
                                                       parallel->info.alias,
-                                                      qemuCaps)))
+                                                      qemuCaps, cmd, driver,
+                                                      fdset,
+                                                      &parallel->info)))
                     goto error;
-                virCommandAddArg(cmd, devstr);
+                virCommandAddArgList(cmd, "-chardev", devstr, NULL);
                 VIR_FREE(devstr);
 
                 virCommandAddArg(cmd, "-device");
@@ -6409,12 +6561,12 @@ qemuBuildCommandLine(virConnectPtr conn,
                 goto error;
             }
 
-            virCommandAddArg(cmd, "-chardev");
             if (!(devstr = qemuBuildChrChardevStr(&channel->source,
                                                   channel->info.alias,
-                                                  qemuCaps)))
+                                                  qemuCaps, cmd, driver, fdset,
+                                                  &channel->info)))
                 goto error;
-            virCommandAddArg(cmd, devstr);
+            virCommandAddArgList(cmd, "-chardev", devstr, NULL);
             VIR_FREE(devstr);
 
             addr = virSocketAddrFormat(channel->target.addr);
@@ -6444,12 +6596,13 @@ qemuBuildCommandLine(virConnectPtr conn,
                  * the newer -chardev interface.  */
                 ;
             } else {
-                virCommandAddArg(cmd, "-chardev");
                 if (!(devstr = qemuBuildChrChardevStr(&channel->source,
                                                       channel->info.alias,
-                                                      qemuCaps)))
+                                                      qemuCaps, cmd, driver,
+                                                      fdset,
+                                                      &channel->info)))
                     goto error;
-                virCommandAddArg(cmd, devstr);
+                virCommandAddArgList(cmd, "-chardev", devstr, NULL);
                 VIR_FREE(devstr);
             }
 
@@ -6482,12 +6635,12 @@ qemuBuildCommandLine(virConnectPtr conn,
                 goto error;
             }
 
-            virCommandAddArg(cmd, "-chardev");
             if (!(devstr = qemuBuildChrChardevStr(&console->source,
                                                   console->info.alias,
-                                                  qemuCaps)))
+                                                  qemuCaps, cmd, driver, fdset,
+                                                  &console->info)))
                 goto error;
-            virCommandAddArg(cmd, devstr);
+            virCommandAddArgList(cmd, "-chardev", devstr, NULL);
             VIR_FREE(devstr);
 
             virCommandAddArg(cmd, "-device");
@@ -6504,12 +6657,12 @@ qemuBuildCommandLine(virConnectPtr conn,
                 goto error;
             }
 
-            virCommandAddArg(cmd, "-chardev");
             if (!(devstr = qemuBuildChrChardevStr(&console->source,
                                                   console->info.alias,
-                                                  qemuCaps)))
+                                                  qemuCaps, cmd, driver, fdset,
+                                                  &console->info)))
                 goto error;
-            virCommandAddArg(cmd, devstr);
+            virCommandAddArgList(cmd, "-chardev", devstr, NULL);
             VIR_FREE(devstr);
 
             virCommandAddArg(cmd, "-device");
@@ -6846,14 +6999,14 @@ qemuBuildCommandLine(virConnectPtr conn,
         virDomainRedirdevDefPtr redirdev = def->redirdevs[i];
         char *devstr;
 
-        virCommandAddArg(cmd, "-chardev");
         if (!(devstr = qemuBuildChrChardevStr(&redirdev->source.chr,
                                               redirdev->info.alias,
-                                              qemuCaps))) {
+                                              qemuCaps, cmd, driver, fdset,
+                                              &redirdev->info))) {
             goto error;
         }
 
-        virCommandAddArg(cmd, devstr);
+        virCommandAddArgList(cmd, "-chardev", devstr, NULL);
         VIR_FREE(devstr);
 
         if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE))
@@ -7079,6 +7232,7 @@ qemuBuildCommandLine(virConnectPtr conn,
  no_memory:
     virReportOOMError();
  error:
+    virFdSetReset(fdset);
     virObjectUnref(cfg);
     /* free up any resources in the network driver */
     for (i = 0; i <= last_good_net; i++)
Index: libvirt/src/qemu/qemu_command.h
===================================================================
--- libvirt.orig/src/qemu/qemu_command.h
+++ libvirt/src/qemu/qemu_command.h
@@ -58,7 +58,8 @@ virCommandPtr qemuBuildCommandLine(virCo
                                    const char *migrateFrom,
                                    int migrateFd,
                                    virDomainSnapshotObjPtr current_snapshot,
-                                   enum virNetDevVPortProfileOp vmop)
+                                   enum virNetDevVPortProfileOp vmop,
+                                   virFdSetPtr fdset);
     ATTRIBUTE_NONNULL(1);
 
 /* Generate string for arch-specific '-device' parameter */
@@ -95,9 +96,16 @@ char *qemuDeviceDriveHostAlias(virDomain
 char *qemuBuildDriveStr(virConnectPtr conn,
                         virDomainDiskDefPtr disk,
                         bool bootable,
-                        virQEMUCapsPtr qemuCaps);
+                        virQEMUCapsPtr qemuCaps,
+                        virCommandPtr cmd,
+                        virQEMUDriverPtr driver,
+                        virFdSetPtr fdset);
+
 char *qemuBuildFSStr(virDomainFSDefPtr fs,
-                     virQEMUCapsPtr qemuCaps);
+                     virQEMUCapsPtr qemuCaps,
+                     virCommandPtr cmd,
+                     virQEMUDriverPtr driver,
+                     virFdSetPtr fdset);
 
 /* Current, best practice */
 char * qemuBuildDriveDevStr(virDomainDefPtr def,
Index: libvirt/src/qemu/qemu_driver.c
===================================================================
--- libvirt.orig/src/qemu/qemu_driver.c
+++ libvirt/src/qemu/qemu_driver.c
@@ -2581,7 +2581,7 @@ qemuCompressProgramName(int compress)
 
 /* Internal function to properly create or open existing files, with
  * ownership affected by qemu driver setup.  */
-static int
+int
 qemuOpenFile(virQEMUDriverPtr driver, const char *path, int oflags,
              bool *needUnlink, bool *bypassSecurityDriver)
 {
@@ -5438,7 +5438,8 @@ static char *qemuDomainXMLToNative(virCo
 
     if (!(cmd = qemuBuildCommandLine(conn, driver, def,
                                      &monConfig, monitor_json, qemuCaps,
-                                     NULL, -1, NULL, VIR_NETDEV_VPORT_PROFILE_OP_NO_OP)))
+                                     NULL, -1, NULL, VIR_NETDEV_VPORT_PROFILE_OP_NO_OP,
+                                     NULL)))
         goto cleanup;
 
     ret = virCommandToString(cmd);
Index: libvirt/src/qemu/qemu_hotplug.c
===================================================================
--- libvirt.orig/src/qemu/qemu_hotplug.c
+++ libvirt/src/qemu/qemu_hotplug.c
@@ -264,7 +264,8 @@ int qemuDomainAttachPciDiskDevice(virCon
         if (qemuAssignDeviceDiskAlias(vm->def, disk, priv->qemuCaps) < 0)
             goto error;
 
-        if (!(drivestr = qemuBuildDriveStr(conn, disk, false, priv->qemuCaps)))
+        if (!(drivestr = qemuBuildDriveStr(conn, disk, false, priv->qemuCaps,
+                                           NULL, driver, priv->fdset)))
             goto error;
 
         if (!(devstr = qemuBuildDriveDevStr(NULL, disk, 0, priv->qemuCaps)))
@@ -321,6 +322,8 @@ cleanup:
     return ret;
 
 error:
+    virFdSetRemoveAlias(priv->fdset, disk->info.alias);
+
     if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_DEVICE) &&
         (disk->info.type == VIR_DOMAIN_DEVICE_ADDRESS_TYPE_PCI) &&
         releaseaddr &&
@@ -504,7 +507,8 @@ int qemuDomainAttachSCSIDisk(virConnectP
             goto error;
     }
 
-    if (!(drivestr = qemuBuildDriveStr(conn, disk, false, priv->qemuCaps)))
+    if (!(drivestr = qemuBuildDriveStr(conn, disk, false, priv->qemuCaps,
+                                       NULL, driver, priv->fdset)))
         goto error;
 
     for (i = 0 ; i <= disk->info.addr.drive.controller ; i++) {
@@ -571,6 +575,8 @@ cleanup:
     return ret;
 
 error:
+    virFdSetRemoveAlias(priv->fdset, disk->info.alias);
+
     if (virSecurityManagerRestoreImageLabel(driver->securityManager,
                                             vm->def, disk) < 0)
         VIR_WARN("Unable to restore security label on %s", disk->src);
@@ -622,7 +628,8 @@ int qemuDomainAttachUsbMassstorageDevice
     if (virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_DEVICE)) {
         if (qemuAssignDeviceDiskAlias(vm->def, disk, priv->qemuCaps) < 0)
             goto error;
-        if (!(drivestr = qemuBuildDriveStr(conn, disk, false, priv->qemuCaps)))
+        if (!(drivestr = qemuBuildDriveStr(conn, disk, false, priv->qemuCaps,
+                                           NULL, driver, priv->fdset)))
             goto error;
         if (!(devstr = qemuBuildDriveDevStr(NULL, disk, 0, priv->qemuCaps)))
             goto error;
@@ -664,6 +671,8 @@ cleanup:
     return ret;
 
 error:
+    virFdSetRemoveAlias(priv->fdset, disk->info.alias);
+
     if (virSecurityManagerRestoreImageLabel(driver->securityManager,
                                             vm->def, disk) < 0)
         VIR_WARN("Unable to restore security label on %s", disk->src);
Index: libvirt/src/qemu/qemu_process.c
===================================================================
--- libvirt.orig/src/qemu/qemu_process.c
+++ libvirt/src/qemu/qemu_process.c
@@ -3894,7 +3894,8 @@ int qemuProcessStart(virConnectPtr conn,
     VIR_DEBUG("Building emulator command line");
     if (!(cmd = qemuBuildCommandLine(conn, driver, vm->def, priv->monConfig,
                                      priv->monJSON != 0, priv->qemuCaps,
-                                     migrateFrom, stdin_fd, snapshot, vmop)))
+                                     migrateFrom, stdin_fd, snapshot, vmop,
+                                     priv->fdset)))
         goto cleanup;
 
     /* now that we know it is about to start call the hook if present */
@@ -4188,6 +4189,7 @@ cleanup:
     virBitmapFree(nodemask);
     virCommandFree(cmd);
     VIR_FORCE_CLOSE(logfile);
+    virFdSetReset(priv->fdset);
     qemuProcessStop(driver, vm, VIR_DOMAIN_SHUTOFF_FAILED, stop_flags);
     virObjectUnref(cfg);
     virObjectUnref(caps);
@@ -4337,7 +4339,7 @@ void qemuProcessStop(virQEMUDriverPtr dr
         priv->monConfig = NULL;
     }
 
-    virFdsetReset(&priv->fdset);
+    virFdSetReset(priv->fdset);
 
     /* shut it off for sure */
     ignore_value(qemuProcessKill(driver, vm, VIR_QEMU_PROCESS_KILL_FORCE|
Index: libvirt/src/qemu/qemu_driver.h
===================================================================
--- libvirt.orig/src/qemu/qemu_driver.h
+++ libvirt/src/qemu/qemu_driver.h
@@ -24,6 +24,10 @@
 #ifndef __QEMU_DRIVER_H__
 # define __QEMU_DRIVER_H__
 
+# include "qemu_conf.h"
+
 int qemuRegister(void);
+int qemuOpenFile(virQEMUDriverPtr driver, const char *path, int oflags,
+                 bool *needUnlink, bool *bypassSecurityDriver);
 
 #endif /* __QEMU_DRIVER_H__ */
Index: libvirt/tests/qemuxml2argvtest.c
===================================================================
--- libvirt.orig/tests/qemuxml2argvtest.c
+++ libvirt/tests/qemuxml2argvtest.c
@@ -13,6 +13,7 @@
 # include "internal.h"
 # include "testutils.h"
 # include "viralloc.h"
+# include "virfdset.h"
 # include "qemu/qemu_capabilities.h"
 # include "qemu/qemu_command.h"
 # include "qemu/qemu_domain.h"
@@ -95,9 +96,12 @@ static int testCompareXMLToArgvFiles(con
     virConnectPtr conn;
     char *log = NULL;
     virCommandPtr cmd = NULL;
+    virFdSetPtr fdset;
 
     if (!(conn = virGetConnect()))
         goto out;
+    if (!(fdset = virFdSetNew()))
+        goto out;
     conn->secretDriver = &fakeSecretDriver;
 
     if (!(vmdef = virDomainDefParseFile(driver.caps, xml,
@@ -154,7 +158,8 @@ static int testCompareXMLToArgvFiles(con
     if (!(cmd = qemuBuildCommandLine(conn, &driver, vmdef, &monitor_chr,
                                      (flags & FLAG_JSON), extraFlags,
                                      migrateFrom, migrateFd, NULL,
-                                     VIR_NETDEV_VPORT_PROFILE_OP_NO_OP))) {
+                                     VIR_NETDEV_VPORT_PROFILE_OP_NO_OP,
+                                     fdset))) {
         if (flags & FLAG_EXPECT_FAILURE) {
             ret = 0;
             virResetLastError();
@@ -201,6 +206,7 @@ out:
     virCommandFree(cmd);
     virDomainDefFree(vmdef);
     virObjectUnref(conn);
+    virFdSetFree(fdset);
     return ret;
 }
 
@@ -882,6 +888,9 @@ mymain(void)
             QEMU_CAPS_DEVICE, QEMU_CAPS_DEVICE_VIDEO_PRIMARY,
             QEMU_CAPS_DEVICE_QXL, QEMU_CAPS_DEVICE_QXL_VGA);
 
+    DO_TEST("add-fd", QEMU_CAPS_ADD_FD,
+            QEMU_CAPS_CHARDEV, QEMU_CAPS_DEVICE, QEMU_CAPS_DRIVE);
+
     virObjectUnref(driver.config);
     virObjectUnref(driver.caps);
     VIR_FREE(map);
Index: libvirt/tests/qemuxml2argvdata/qemuxml2argv-add-fd.args
===================================================================
--- /dev/null
+++ libvirt/tests/qemuxml2argvdata/qemuxml2argv-add-fd.args
@@ -0,0 +1,23 @@
+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test \
+/usr/bin/qemu -S -M pc -m 214 -smp 1 -nographic -nodefaults \
+-chardev socket,id=charmonitor,path=/tmp/test-monitor,server,nowait \
+-mon chardev=charmonitor,id=monitor,mode=readline -no-acpi -boot c -usb \
+\
+-add-fd set=1,fd=3,opaque=RDONLY:/dev/null \
+-add-fd set=1,fd=4,opaque=RDWR:/dev/null \
+-drive file=/dev/fdset/1,if=none,id=drive-ide0-0-0 \
+-device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
+\
+-add-fd set=2,fd=5,opaque=RDWR:/dev/null \
+-chardev tty,id=charserial0,path=/dev/fdset/2 \
+-device isa-serial,chardev=charserial0,id=serial0 \
+\
+-add-fd set=3,fd=6,opaque=RDWR:/dev/null \
+-chardev pipe,id=charserial1,path=/dev/fdset/3 \
+-device isa-serial,chardev=charserial1,id=serial1 \
+\
+-add-fd set=4,fd=7,opaque=RDWR:/dev/null \
+-chardev parport,id=charparallel0,path=/dev/fdset/4 \
+-device isa-parallel,chardev=charparallel0,id=parallel0 \
+\
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3
Index: libvirt/tests/qemuxml2argvdata/qemuxml2argv-add-fd.xml
===================================================================
--- /dev/null
+++ libvirt/tests/qemuxml2argvdata/qemuxml2argv-add-fd.xml
@@ -0,0 +1,36 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219100</memory>
+  <currentMemory unit='KiB'>219100</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <disk type='file' device='disk'>
+      <driver name='qemu' type='raw'/>
+      <source file='/dev/null'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <serial type='dev'>
+      <source path='/dev/null'/>
+      <target port='0'/>
+    </serial>
+    <serial type='pipe'>
+      <source path='/dev/null'/>
+      <target port='1'/>
+    </serial>
+    <parallel type='dev'>
+      <source path='/dev/null'/>
+      <target port='0'/>
+    </parallel>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>
Index: libvirt/tests/qemuxmlnstest.c
===================================================================
--- libvirt.orig/tests/qemuxmlnstest.c
+++ libvirt/tests/qemuxmlnstest.c
@@ -41,10 +41,14 @@ static int testCompareXMLToArgvFiles(con
     char *log = NULL;
     char *emulator = NULL;
     virCommandPtr cmd = NULL;
+    virFdSetPtr fdset;
 
     if (!(conn = virGetConnect()))
         goto fail;
 
+    if (!(fdset = virFdSetNew()))
+        goto fail;
+
     len = virtTestLoadFile(cmdline, &expectargv);
     if (len < 0)
         goto fail;
@@ -110,7 +114,8 @@ static int testCompareXMLToArgvFiles(con
     if (!(cmd = qemuBuildCommandLine(conn, &driver,
                                      vmdef, &monitor_chr, json, extraFlags,
                                      migrateFrom, migrateFd, NULL,
-                                     VIR_NETDEV_VPORT_PROFILE_OP_NO_OP)))
+                                     VIR_NETDEV_VPORT_PROFILE_OP_NO_OP,
+                                     fdset)))
         goto fail;
 
     if (!!virGetLastError() != expectError) {
@@ -150,6 +155,7 @@ static int testCompareXMLToArgvFiles(con
     VIR_FREE(actualargv);
     virCommandFree(cmd);
     virDomainDefFree(vmdef);
+    virFdSetFree(fdset);
     virObjectUnref(conn);
     return ret;
 }