diff -rup libvirt-0.7.1/src/hostusb.c new/src/hostusb.c
--- libvirt-0.7.1/src/hostusb.c	2010-05-17 16:53:48.740748000 -0400
+++ new/src/hostusb.c	2010-05-17 16:57:19.294731000 -0400
@@ -37,9 +37,10 @@
 #include "util.h"
 #include "virterror_internal.h"
 
+#define USB_SYSFS "/sys/bus/usb"
 #define USB_DEVFS "/dev/bus/usb/"
-#define USB_ID_LEN 10 /* "XXXX XXXX" */
-#define USB_ADDR_LEN 8 /* "XXX:XXX" */
+#define USB_ID_LEN 10 /* "1234 5678" */
+#define USB_ADDR_LEN 8 /* "123:456" */
 
 struct _usbDevice {
     unsigned      bus;
@@ -57,6 +58,101 @@ struct _usbDevice {
     virReportErrorHelper(conn, VIR_FROM_NONE, code, __FILE__,  \
                          __FUNCTION__, __LINE__, fmt)
 
+static int usbSysReadFile(virConnectPtr conn,
+                          const char *f_name, const char *d_name,
+                          int base, unsigned *value)
+{
+    int ret = -1, tmp;
+    char *buf = NULL;
+    char *filename = NULL;
+    char *ignore = NULL;
+
+    tmp = virAsprintf(&filename, USB_SYSFS "/devices/%s/%s", d_name, f_name);
+    if (tmp < 0) {
+        virReportOOMError(conn);
+        goto error;
+    }
+
+    if (virFileReadAll(filename, 1024, &buf) < 0)
+        goto error;
+
+    if (virStrToLong_ui(buf, &ignore, base, value) < 0) {
+        usbReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                       _("Could not parse usb file %s"), filename);
+        goto error;
+    }
+
+    ret = 0;
+error:
+    VIR_FREE(filename);
+    VIR_FREE(buf);
+    return ret;
+}
+
+static int usbFindBusByVendor(virConnectPtr conn,
+                              unsigned vendor, unsigned product,
+                              unsigned *bus, unsigned *devno)
+{
+    DIR *dir = NULL;
+    int ret = -1, found = 0;
+    char *ignore = NULL;
+    struct dirent *de;
+
+    dir = opendir(USB_SYSFS "/devices");
+    if (!dir) {
+        virReportSystemError(conn, errno,
+                             _("Could not open directory %s"),
+                             USB_SYSFS "/devices");
+        goto error;
+    }
+
+    while ((de = readdir(dir))) {
+        unsigned found_prod, found_vend;
+        if (de->d_name[0] == '.' || strchr(de->d_name, ':'))
+            continue;
+
+        if (usbSysReadFile(conn, "idVendor", de->d_name,
+                           16, &found_vend) < 0)
+            goto error;
+        if (usbSysReadFile(conn, "idProduct", de->d_name,
+                           16, &found_prod) < 0)
+            goto error;
+
+        if (found_prod == product && found_vend == vendor) {
+            /* Lookup bus.addr info */
+            char *tmpstr = de->d_name;
+            unsigned found_bus, found_addr;
+
+            if (STREQ(de->d_name, "usb"))
+                tmpstr += 3;
+
+            if (virStrToLong_ui(tmpstr, &ignore, 10, &found_bus) < 0) {
+                usbReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                               _("Failed to parse dir name '%s'"),
+                               de->d_name);
+                goto error;
+            }
+
+            if (usbSysReadFile(conn, "devnum", de->d_name,
+                               10, &found_addr) < 0)
+                goto error;
+
+            *bus = found_bus;
+            *devno = found_addr;
+            found = 1;
+            break;
+        }
+    }
+
+    if (!found)
+        usbReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                       _("Did not find USB device %x:%x"), vendor, product);
+    else
+        ret = 0;
+
+error:
+    return ret;
+}
 
 usbDevice *
 usbGetDevice(virConnectPtr conn,
@@ -86,6 +182,21 @@ usbGetDevice(virConnectPtr conn,
     return dev;
 }
 
+
+usbDevice *
+usbFindDevice(unsigned vendor,
+              unsigned product)
+{
+    unsigned bus = 0, devno = 0;
+
+    if (usbFindBusByVendor(vendor, product, &bus, &devno) < 0) {
+        return NULL;
+    }
+
+    return usbGetDevice(bus, devno);
+}
+
+
 void
 usbFreeDevice(virConnectPtr conn ATTRIBUTE_UNUSED, usbDevice *dev)
 {
@@ -93,6 +204,18 @@ usbFreeDevice(virConnectPtr conn ATTRIBU
     VIR_FREE(dev);
 }
 
+unsigned usbDeviceGetBus(usbDevice *dev)
+{
+    return dev->bus;
+}
+
+
+unsigned usbDeviceGetDevno(usbDevice *dev)
+{
+    return dev->dev;
+}
+
+
 
 int usbDeviceFileIterate(virConnectPtr conn,
                          usbDevice *dev,
diff -rup libvirt-0.7.1/src/hostusb.h new/src/hostusb.h
--- libvirt-0.7.1/src/hostusb.h	2009-09-10 09:45:00.000000000 -0400
+++ new/src/hostusb.h	2010-05-17 16:58:06.553924000 -0400
@@ -27,11 +27,16 @@
 
 typedef struct _usbDevice usbDevice;
 
-usbDevice *usbGetDevice      (virConnectPtr  conn,
-                              unsigned       bus,
-                              unsigned       devno);
-void       usbFreeDevice     (virConnectPtr  conn,
-                              usbDevice     *dev);
+usbDevice *usbGetDevice(virConnectPtr conn,
+                        unsigned bus,
+                        unsigned devno);
+usbDevice *usbFindDevice(virConnectPtr conn,
+                         unsigned vendor,
+                         unsigned product);
+void       usbFreeDevice (virConnectPtr conn, usbDevice *dev);
+
+unsigned usbDeviceGetBus(usbDevice *dev);
+unsigned usbDeviceGetDevno(usbDevice *dev);
 
 /*
  * Callback that will be invoked once for each file
diff -rup libvirt-0.7.1/src/libvirt_private.syms new/src/libvirt_private.syms
--- libvirt-0.7.1/src/libvirt_private.syms	2010-05-17 16:53:48.401831000 -0400
+++ new/src/libvirt_private.syms	2010-05-17 16:55:03.001748000 -0400
@@ -441,7 +441,10 @@ virFileMatchesNameSuffix;
 
 # usb.h
 usbGetDevice;
+usbFindDevice;
 usbFreeDevice;
+usbDeviceGetBus;
+usbDeviceGetDevno;
 usbDeviceFileIterate;
 
 # uuid.h
diff -rup libvirt-0.7.1/src/qemu_driver.c new/src/qemu_driver.c
--- libvirt-0.7.1/src/qemu_driver.c	2010-05-17 16:53:48.785743000 -0400
+++ new/src/qemu_driver.c	2010-05-17 17:06:40.575145000 -0400
@@ -1493,16 +1493,13 @@ qemuUpdateActivePciHostdevs(struct qemud
 }
 
 static int
-qemuPrepareHostDevices(virConnectPtr conn,
-                       struct qemud_driver *driver,
-                       virDomainDefPtr def)
+qemuPrepareHostPCIDevices(virConnectPtr conn,
+                          struct qemud_driver *driver,
+                          virDomainDefPtr def)
 {
     pciDeviceList *pcidevs;
     int i;
 
-    if (!def->nhostdevs)
-        return 0;
-
     if (!(pcidevs = qemuGetPciHostDeviceList(conn, def)))
         return -1;
 
@@ -1792,14 +1789,11 @@ static int qemuDomainSetHostdevUSBOwners
     struct qemuFileOwner owner = { uid, gid };
     int ret = -1;
 
-    /* XXX what todo for USB devs assigned based on product/vendor ? Doom :-( */
-    if (!def->source.subsys.u.usb.bus ||
-        !def->source.subsys.u.usb.device)
-        return 0;
-
     usbDevice *dev = usbGetDevice(conn,
                                   def->source.subsys.u.usb.bus,
-                                  def->source.subsys.u.usb.device);
+                                  def->source.subsys.u.usb.device,
+                                  def->source.subsys.u.usb.vendor,
+                                  def->source.subsys.u.usb.product);
 
     if (!dev)
         goto cleanup;
@@ -2065,13 +2059,17 @@ static int qemudStartVMDaemon(virConnect
         return -1;
     }
 
+    DEBUG0("Preparing host devices");
+    if (qemuPrepareHostDevices(conn, driver, vm->def) < 0)
+        goto cleanup;
+
     /* If you are using a SecurityDriver with dynamic labelling,
        then generate a security label for isolation */
     if (vm->def->seclabel.type == VIR_DOMAIN_SECLABEL_DYNAMIC &&
         driver->securityDriver &&
         driver->securityDriver->domainGenSecurityLabel &&
         driver->securityDriver->domainGenSecurityLabel(conn, vm) < 0)
-        return -1;
+        return cleanup;
 
     /* Ensure no historical cgroup for this VM is lieing around bogus settings */
     qemuRemoveCgroup(conn, driver, vm);
@@ -2119,9 +2117,6 @@ static int qemudStartVMDaemon(virConnect
     if (qemuSetupCgroup(conn, driver, vm) < 0)
         goto cleanup;
 
-    if (qemuPrepareHostDevices(conn, driver, vm->def) < 0)
-        goto cleanup;
-
     if (VIR_ALLOC(vm->monitor_chr) < 0) {
         virReportOOMError(conn);
         goto cleanup;
@@ -2348,6 +2343,56 @@ retry:
 }
 
 
+
+static int
+qemuPrepareHostUSBDevices(struct qemud_driver *driver ATTRIBUTE_UNUSED,
+                          virDomainDefPtr def)
+{
+    int i;
+    for (i = 0 ; i < def->nhostdevs ; i++) {
+        virDomainHostdevDefPtr hostdev = def->hostdevs[i];
+
+        if (hostdev->mode != VIR_DOMAIN_HOSTDEV_MODE_SUBSYS)
+            continue;
+        if (hostdev->source.subsys.type != VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_USB)
+            continue;
+
+        /* Resolve a vendor/product to bus/device */
+        if (hostdev->source.subsys.u.usb.vendor) {
+            usbDevice *usb
+                = usbFindDevice(hostdev->source.subsys.u.usb.vendor,
+                                hostdev->source.subsys.u.usb.product);
+
+            if (!usb)
+                return -1;
+
+            hostdev->source.subsys.u.usb.bus = usbDeviceGetBus(usb);
+            hostdev->source.subsys.u.usb.device = usbDeviceGetDevno(usb);
+
+            usbFreeDevice(usb);
+        }
+    }
+
+    return 0;
+}
+
+static int
+qemuPrepareHostDevices(struct qemud_driver *driver,
+                       virDomainDefPtr def)
+{
+    if (!def->nhostdevs)
+        return 0;
+
+    if (qemuPrepareHostPCIDevices(driver, def) < 0)
+        return -1;
+
+    if (qemuPrepareHostUSBDevices(driver, def) < 0)
+        return -1;
+
+    return 0;
+}
+
+
 static void
 qemudDispatchVMEvent(int watch, int fd, int events, void *opaque) {
     struct qemud_driver *driver = opaque;
@@ -6294,6 +6339,23 @@ static int qemudDomainDetachHostDevice(v
         return -1;
     }
 
+    /* Resolve USB product/vendor to bus/device */
+    if (hostdev->source.subsys.type == VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_USB &&
+        hostdev->source.subsys.u.usb.vendor) {
+        usbDevice *usb
+            = usbFindDevice(hostdev->source.subsys.u.usb.vendor,
+                            hostdev->source.subsys.u.usb.product);
+
+        if (!usb)
+            return -1;
+
+        hostdev->source.subsys.u.usb.bus = usbDeviceGetBus(usb);
+        hostdev->source.subsys.u.usb.device = usbDeviceGetDevno(usb);
+
+        usbFreeDevice(usb);
+    }
+
+
     if (driver->securityDriver &&
         driver->securityDriver->domainSetSecurityHostdevLabel(conn, vm, dev->data.hostdev) < 0)
         VIR_WARN0("Failed to restore device labelling");
diff -rup libvirt-0.7.1/src/security_selinux.c new/src/security_selinux.c
--- libvirt-0.7.1/src/security_selinux.c	2010-05-17 16:53:48.775745000 -0400
+++ new/src/security_selinux.c	2010-05-17 16:58:47.442604000 -0400
@@ -482,20 +482,15 @@ SELinuxSetSecurityHostdevLabel(virConnec
 
     switch (dev->source.subsys.type) {
     case VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_USB: {
-        if (dev->source.subsys.u.usb.bus && dev->source.subsys.u.usb.device) {
-            usbDevice *usb = usbGetDevice(conn,
-                                          dev->source.subsys.u.usb.bus,
-                                          dev->source.subsys.u.usb.device);
-
-            if (!usb)
-                goto done;
-
-            ret = usbDeviceFileIterate(conn, usb, SELinuxSetSecurityUSBLabel, vm);
-            usbFreeDevice(conn, usb);
-        } else {
-            /* XXX deal with product/vendor better */
-            ret = 0;
-        }
+        usbDevice *usb = usbGetDevice(conn,
+                                      dev->source.subsys.u.usb.bus,
+                                      dev->source.subsys.u.usb.device);
+
+        if (!usb)
+            goto done;
+
+        ret = usbDeviceFileIterate(conn, usb, SELinuxSetSecurityUSBLabel, vm);
+        usbFreeDevice(conn, usb);
         break;
     }
 
diff -rup libvirt-0.7.1/src/hostusb.c new/src/hostusb.c
--- libvirt-0.7.1/src/hostusb.c	2010-05-17 17:09:02.573638000 -0400
+++ new/src/hostusb.c	2010-05-17 17:29:49.133509000 -0400
@@ -184,16 +184,17 @@ usbGetDevice(virConnectPtr conn,
 
 
 usbDevice *
-usbFindDevice(unsigned vendor,
+usbFindDevice(virConnectPtr conn,
+              unsigned vendor,
               unsigned product)
 {
     unsigned bus = 0, devno = 0;
 
-    if (usbFindBusByVendor(vendor, product, &bus, &devno) < 0) {
+    if (usbFindBusByVendor(conn, vendor, product, &bus, &devno) < 0) {
         return NULL;
     }
 
-    return usbGetDevice(bus, devno);
+    return usbGetDevice(conn, bus, devno);
 }
 
 
diff -rup libvirt-0.7.1/src/qemu_driver.c new/src/qemu_driver.c
--- libvirt-0.7.1/src/qemu_driver.c	2010-05-17 17:09:02.602638000 -0400
+++ new/src/qemu_driver.c	2010-05-17 17:36:10.066214000 -0400
@@ -1791,9 +1791,7 @@ static int qemuDomainSetHostdevUSBOwners
 
     usbDevice *dev = usbGetDevice(conn,
                                   def->source.subsys.u.usb.bus,
-                                  def->source.subsys.u.usb.device,
-                                  def->source.subsys.u.usb.vendor,
-                                  def->source.subsys.u.usb.product);
+                                  def->source.subsys.u.usb.device);
 
     if (!dev)
         goto cleanup;
@@ -2026,6 +2024,10 @@ qemuPrepareMonitorChr(virConnectPtr conn
     return 0;
 }
 
+static int
+qemuPrepareHostDevices(struct qemud_driver *driver,
+                       virDomainDefPtr def);
+
 static int qemudStartVMDaemon(virConnectPtr conn,
                               struct qemud_driver *driver,
                               virDomainObjPtr vm,
@@ -2060,7 +2062,7 @@ static int qemudStartVMDaemon(virConnect
     }
 
     DEBUG0("Preparing host devices");
-    if (qemuPrepareHostDevices(conn, driver, vm->def) < 0)
+    if (qemuPrepareHostDevices(driver, vm->def) < 0)
         goto cleanup;
 
     /* If you are using a SecurityDriver with dynamic labelling,
@@ -2069,7 +2071,7 @@ static int qemudStartVMDaemon(virConnect
         driver->securityDriver &&
         driver->securityDriver->domainGenSecurityLabel &&
         driver->securityDriver->domainGenSecurityLabel(conn, vm) < 0)
-        return cleanup;
+        goto cleanup;
 
     /* Ensure no historical cgroup for this VM is lieing around bogus settings */
     qemuRemoveCgroup(conn, driver, vm);
@@ -2360,7 +2362,8 @@ qemuPrepareHostUSBDevices(struct qemud_d
         /* Resolve a vendor/product to bus/device */
         if (hostdev->source.subsys.u.usb.vendor) {
             usbDevice *usb
-                = usbFindDevice(hostdev->source.subsys.u.usb.vendor,
+                = usbFindDevice(NULL,
+                                hostdev->source.subsys.u.usb.vendor,
                                 hostdev->source.subsys.u.usb.product);
 
             if (!usb)
@@ -2369,7 +2372,7 @@ qemuPrepareHostUSBDevices(struct qemud_d
             hostdev->source.subsys.u.usb.bus = usbDeviceGetBus(usb);
             hostdev->source.subsys.u.usb.device = usbDeviceGetDevno(usb);
 
-            usbFreeDevice(usb);
+            usbFreeDevice(NULL, usb);
         }
     }
 
@@ -2383,7 +2386,7 @@ qemuPrepareHostDevices(struct qemud_driv
     if (!def->nhostdevs)
         return 0;
 
-    if (qemuPrepareHostPCIDevices(driver, def) < 0)
+    if (qemuPrepareHostPCIDevices(NULL, driver, def) < 0)
         return -1;
 
     if (qemuPrepareHostUSBDevices(driver, def) < 0)
@@ -6343,7 +6346,8 @@ static int qemudDomainDetachHostDevice(v
     if (hostdev->source.subsys.type == VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_USB &&
         hostdev->source.subsys.u.usb.vendor) {
         usbDevice *usb
-            = usbFindDevice(hostdev->source.subsys.u.usb.vendor,
+            = usbFindDevice(NULL,
+                            hostdev->source.subsys.u.usb.vendor,
                             hostdev->source.subsys.u.usb.product);
 
         if (!usb)
@@ -6352,7 +6356,7 @@ static int qemudDomainDetachHostDevice(v
         hostdev->source.subsys.u.usb.bus = usbDeviceGetBus(usb);
         hostdev->source.subsys.u.usb.device = usbDeviceGetDevno(usb);
 
-        usbFreeDevice(usb);
+        usbFreeDevice(NULL, usb);
     }