diff --git a/hw/usb/hcd-ehci.c b/hw/usb/hcd-ehci.c
index 9ca7b87a80..56ab2f457f 100644
--- a/hw/usb/hcd-ehci.c
+++ b/hw/usb/hcd-ehci.c
@@ -1838,6 +1838,9 @@ static int ehci_state_fetchqtd(EHCIQueue *q)
             ehci_set_state(q->ehci, q->async, EST_EXECUTING);
             break;
         }
+    } else if (q->dev == NULL) {
+        ehci_trace_guest_bug(q->ehci, "no device attached to queue");
+        ehci_set_state(q->ehci, q->async, EST_HORIZONTALQH);
     } else {
         p = ehci_alloc_packet(q);
         p->qtdaddr = q->qtdaddr;
diff --git a/hw/usb/hcd-xhci.c b/hw/usb/hcd-xhci.c
index f698224c8a..f578264948 100644
--- a/hw/usb/hcd-xhci.c
+++ b/hw/usb/hcd-xhci.c
@@ -2543,6 +2543,9 @@ static void xhci_process_commands(XHCIState *xhci)
         case CR_GET_PORT_BANDWIDTH:
             event.ccode = xhci_get_port_bandwidth(xhci, trb.parameter);
             break;
+        case CR_NOOP:
+            event.ccode = CC_SUCCESS;
+            break;
         case CR_VENDOR_NEC_FIRMWARE_REVISION:
             if (xhci->nec_quirks) {
                 event.type = 48; /* NEC reply */
diff --git a/hw/usb/redirect.c b/hw/usb/redirect.c
index fc9fe0c00f..e0f5ca6f81 100644
--- a/hw/usb/redirect.c
+++ b/hw/usb/redirect.c
@@ -819,8 +819,8 @@ static void usbredir_handle_interrupt_in_data(USBRedirDevice *dev,
                                               USBPacket *p, uint8_t ep)
 {
     /* Input interrupt endpoint, buffered packet input */
-    struct buf_packet *intp;
-    int status, len;
+    struct buf_packet *intp, *intp_to_free;
+    int status, len, sum;
 
     if (!dev->endpoint[EP2I(ep)].interrupt_started &&
             !dev->endpoint[EP2I(ep)].interrupt_error) {
@@ -839,9 +839,17 @@ static void usbredir_handle_interrupt_in_data(USBRedirDevice *dev,
         dev->endpoint[EP2I(ep)].bufpq_dropping_packets = 0;
     }
 
-    intp = QTAILQ_FIRST(&dev->endpoint[EP2I(ep)].bufpq);
+    /* check for completed interrupt message (with all fragments) */
+    sum = 0;
+    QTAILQ_FOREACH(intp, &dev->endpoint[EP2I(ep)].bufpq, next) {
+        sum += intp->len;
+        if (intp->len < dev->endpoint[EP2I(ep)].max_packet_size ||
+            sum >= p->iov.size)
+            break;
+    }
+
     if (intp == NULL) {
-        DPRINTF2("interrupt-token-in ep %02X, no intp\n", ep);
+        DPRINTF2("interrupt-token-in ep %02X, no intp, buffered %d\n", ep, sum);
         /* Check interrupt_error for stream errors */
         status = dev->endpoint[EP2I(ep)].interrupt_error;
         dev->endpoint[EP2I(ep)].interrupt_error = 0;
@@ -852,18 +860,42 @@ static void usbredir_handle_interrupt_in_data(USBRedirDevice *dev,
         }
         return;
     }
-    DPRINTF("interrupt-token-in ep %02X status %d len %d\n", ep,
-            intp->status, intp->len);
 
-    status = intp->status;
-    len = intp->len;
-    if (len > p->iov.size) {
-        ERROR("received int data is larger then packet ep %02X\n", ep);
-        len = p->iov.size;
-        status = usb_redir_babble;
+    /* copy of completed interrupt message */
+    sum = 0;
+    status = usb_redir_success;
+    intp_to_free = NULL;
+    QTAILQ_FOREACH(intp, &dev->endpoint[EP2I(ep)].bufpq, next) {
+        if (intp_to_free) {
+            bufp_free(dev, intp_to_free, ep);
+        }
+        DPRINTF("interrupt-token-in ep %02X fragment status %d len %d\n", ep,
+                intp->status, intp->len);
+
+        sum += intp->len;
+        len = intp->len;
+        if (status == usb_redir_success) {
+            status = intp->status;
+        }
+        if (sum > p->iov.size) {
+            ERROR("received int data is larger then packet ep %02X\n", ep);
+            len -= (sum - p->iov.size);
+            sum = p->iov.size;
+            status = usb_redir_babble;
+        }
+
+        usb_packet_copy(p, intp->data, len);
+
+        intp_to_free = intp;
+        if (intp->len < dev->endpoint[EP2I(ep)].max_packet_size ||
+            sum >= p->iov.size)
+            break;
     }
-    usb_packet_copy(p, intp->data, len);
-    bufp_free(dev, intp, ep);
+    if (intp_to_free) {
+        bufp_free(dev, intp_to_free, ep);
+    }
+    DPRINTF("interrupt-token-in ep %02X summary status %d len %d\n", ep,
+            status, sum);
     usbredir_handle_status(dev, p, status);
 }
 
@@ -1499,6 +1531,11 @@ static void usbredir_check_bulk_receiving(USBRedirDevice *dev)
     for (i = EP2I(USB_DIR_IN); i < MAX_ENDPOINTS; i++) {
         dev->endpoint[i].bulk_receiving_enabled = 0;
     }
+
+    if (dev->interface_info.interface_count == NO_INTERFACE_INFO) {
+        return;
+    }
+
     for (i = 0; i < dev->interface_info.interface_count; i++) {
         quirks = usb_get_quirks(dev->device_info.vendor_id,
                                 dev->device_info.product_id,
@@ -2036,22 +2073,17 @@ static void usbredir_interrupt_packet(void *priv, uint64_t id,
     }
 
     if (ep & USB_DIR_IN) {
-        bool q_was_empty;
-
         if (dev->endpoint[EP2I(ep)].interrupt_started == 0) {
             DPRINTF("received int packet while not started ep %02X\n", ep);
             free(data);
             return;
         }
 
-        q_was_empty = QTAILQ_EMPTY(&dev->endpoint[EP2I(ep)].bufpq);
-
         /* bufp_alloc also adds the packet to the ep queue */
         bufp_alloc(dev, data, data_len, interrupt_packet->status, ep, data);
 
-        if (q_was_empty) {
-            usb_wakeup(usb_ep_get(&dev->dev, USB_TOKEN_IN, ep & 0x0f), 0);
-        }
+        /* insufficient data solved with USB_RET_NAK */
+        usb_wakeup(usb_ep_get(&dev->dev, USB_TOKEN_IN, ep & 0x0f), 0);
     } else {
         /*
          * We report output interrupt packets as completed directly upon
diff --git a/qemu-options.hx b/qemu-options.hx
index a308e5f5aa..ea0638e92d 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1436,12 +1436,15 @@ STEXI
 ETEXI
 
 DEF("usb", 0, QEMU_OPTION_usb,
-    "-usb            enable the USB driver (if it is not used by default yet)\n",
+    "-usb            enable on-board USB host controller (if not enabled by default)\n",
     QEMU_ARCH_ALL)
 STEXI
 @item -usb
 @findex -usb
-Enable the USB driver (if it is not used by default yet).
+Enable USB emulation on machine types with an on-board USB host controller (if
+not enabled by default).  Note that on-board USB host controllers may not
+support USB 3.0.  In this case @option{-device qemu-xhci} can be used instead
+on machines with PCI.
 ETEXI
 
 DEF("usbdevice", HAS_ARG, QEMU_OPTION_usbdevice,