usb: use iovecs in USBPacket

Zap data pointer from USBPacket, add a QEMUIOVector instead.
Add a bunch of helper functions to manage USBPacket data.
Switch over users to the new interface.

Note that USBPacket->len was used for two purposes:  First to
pass in the buffer size and second to return the number of
transfered bytes or the status code on async transfers.  There
is a new result variable for the latter.  A new status code
was added to catch uninitialized result.

Nobody creates iovecs with more than one element (yet).
Some users are (temporarely) limited to iovecs with a single
element to keep the patch size as small as possible.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

17 files changed, 288 insertions, 181 deletions

diff --git a/hw/bt-hid.c b/hw/bt-hid.c
index 09120af..a4204f9 100644
--- a/hw/bt-hid.c
+++ b/hw/bt-hid.c
@@ -127,11 +127,11 @@ static int bt_hid_out(struct bt_hid_device_s *s)
     USBPacket p;
 
     if (s->data_type == BT_DATA_OUTPUT) {
-        p.pid = USB_TOKEN_OUT;
-        p.devep = 1;
-        p.data = s->dataout.buffer;
-        p.len = s->dataout.len;
+        usb_packet_init(&p);
+        usb_packet_setup(&p, USB_TOKEN_OUT, 0, 1);
+        usb_packet_addbuf(&p, s->dataout.buffer, s->dataout.len);
         s->dataout.len = s->usbdev->info->handle_data(s->usbdev, &p);
+        usb_packet_cleanup(&p);
 
         return s->dataout.len;
     }
@@ -150,11 +150,11 @@ static int bt_hid_in(struct bt_hid_device_s *s)
 {
     USBPacket p;
 
-    p.pid = USB_TOKEN_IN;
-    p.devep = 1;
-    p.data = s->datain.buffer;
-    p.len = sizeof(s->datain.buffer);
+    usb_packet_init(&p);
+    usb_packet_setup(&p, USB_TOKEN_IN, 0, 1);
+    usb_packet_addbuf(&p, s->dataout.buffer, sizeof(s->datain.buffer));
     s->datain.len = s->usbdev->info->handle_data(s->usbdev, &p);
+    usb_packet_cleanup(&p);
 
     return s->datain.len;
 }
diff --git a/hw/milkymist-softusb.c b/hw/milkymist-softusb.c
index abf7b59..75c85ae 100644
--- a/hw/milkymist-softusb.c
+++ b/hw/milkymist-softusb.c
@@ -234,11 +234,11 @@ static void softusb_usbdev_datain(void *opaque)
 
     USBPacket p;
 
-    p.pid = USB_TOKEN_IN;
-    p.devep = 1;
-    p.data = s->kbd_usb_buffer;
-    p.len = sizeof(s->kbd_usb_buffer);
+    usb_packet_init(&p);
+    usb_packet_setup(&p, USB_TOKEN_IN, 0, 1);
+    usb_packet_addbuf(&p, s->kbd_usb_buffer, sizeof(s->kbd_usb_buffer));
     s->usbdev->info->handle_data(s->usbdev, &p);
+    usb_packet_cleanup(&p);
 
     softusb_kbd_changed(s);
 }
diff --git a/hw/usb-bt.c b/hw/usb-bt.c
index 4557802..529fa33 100644
--- a/hw/usb-bt.c
+++ b/hw/usb-bt.c
@@ -294,9 +294,9 @@ static inline int usb_bt_fifo_dequeue(struct usb_hci_in_fifo_s *fifo,
     if (likely(!fifo->len))
         return USB_RET_STALL;
 
-    len = MIN(p->len, fifo->fifo[fifo->start].len);
-    memcpy(p->data, fifo->fifo[fifo->start].data, len);
-    if (len == p->len) {
+    len = MIN(p->iov.size, fifo->fifo[fifo->start].len);
+    usb_packet_copy(p, fifo->fifo[fifo->start].data, len);
+    if (len == p->iov.size) {
         fifo->fifo[fifo->start].len -= len;
         fifo->fifo[fifo->start].data += len;
     } else {
@@ -319,20 +319,13 @@ static inline void usb_bt_fifo_out_enqueue(struct USBBtState *s,
                 struct usb_hci_out_fifo_s *fifo,
                 void (*send)(struct HCIInfo *, const uint8_t *, int),
                 int (*complete)(const uint8_t *, int),
-                const uint8_t *data, int len)
+                USBPacket *p)
 {
-    if (fifo->len) {
-        memcpy(fifo->data + fifo->len, data, len);
-        fifo->len += len;
-        if (complete(fifo->data, fifo->len)) {
-            send(s->hci, fifo->data, fifo->len);
-            fifo->len = 0;
-        }
-    } else if (complete(data, len))
-        send(s->hci, data, len);
-    else {
-        memcpy(fifo->data, data, len);
-        fifo->len = len;
+    usb_packet_copy(p, fifo->data + fifo->len, p->iov.size);
+    fifo->len += p->iov.size;
+    if (complete(fifo->data, fifo->len)) {
+        send(s->hci, fifo->data, fifo->len);
+        fifo->len = 0;
     }
 
     /* TODO: do we need to loop? */
@@ -432,7 +425,7 @@ static int usb_bt_handle_control(USBDevice *dev, USBPacket *p,
     case ((USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_DEVICE) << 8):
         if (s->config)
             usb_bt_fifo_out_enqueue(s, &s->outcmd, s->hci->cmd_send,
-                            usb_bt_hci_cmd_complete, data, length);
+                            usb_bt_hci_cmd_complete, p);
         break;
     default:
     fail:
@@ -474,12 +467,12 @@ static int usb_bt_handle_data(USBDevice *dev, USBPacket *p)
         switch (p->devep & 0xf) {
         case USB_ACL_EP:
             usb_bt_fifo_out_enqueue(s, &s->outacl, s->hci->acl_send,
-                            usb_bt_hci_acl_complete, p->data, p->len);
+                            usb_bt_hci_acl_complete, p);
             break;
 
         case USB_SCO_EP:
             usb_bt_fifo_out_enqueue(s, &s->outsco, s->hci->sco_send,
-                            usb_bt_hci_sco_complete, p->data, p->len);
+                            usb_bt_hci_sco_complete, p);
             break;
 
         default:
diff --git a/hw/usb-ccid.c b/hw/usb-ccid.c
index 4dda2c4..66aeb21 100644
--- a/hw/usb-ccid.c
+++ b/hw/usb-ccid.c
@@ -934,16 +934,16 @@ static int ccid_handle_bulk_out(USBCCIDState *s, USBPacket *p)
 {
     CCID_Header *ccid_header;
 
-    if (p->len + s->bulk_out_pos > BULK_OUT_DATA_SIZE) {
+    if (p->iov.size + s->bulk_out_pos > BULK_OUT_DATA_SIZE) {
         return USB_RET_STALL;
     }
     ccid_header = (CCID_Header *)s->bulk_out_data;
-    memcpy(s->bulk_out_data + s->bulk_out_pos, p->data, p->len);
-    s->bulk_out_pos += p->len;
-    if (p->len == CCID_MAX_PACKET_SIZE) {
+    usb_packet_copy(p, s->bulk_out_data + s->bulk_out_pos, p->iov.size);
+    s->bulk_out_pos += p->iov.size;
+    if (p->iov.size == CCID_MAX_PACKET_SIZE) {
         DPRINTF(s, D_VERBOSE,
-            "usb-ccid: bulk_in: expecting more packets (%d/%d)\n",
-            p->len, ccid_header->dwLength);
+            "usb-ccid: bulk_in: expecting more packets (%zd/%d)\n",
+            p->iov.size, ccid_header->dwLength);
         return 0;
     }
     if (s->bulk_out_pos < 10) {
@@ -1006,15 +1006,17 @@ static int ccid_handle_bulk_out(USBCCIDState *s, USBPacket *p)
     return 0;
 }
 
-static int ccid_bulk_in_copy_to_guest(USBCCIDState *s, uint8_t *data, int len)
+static int ccid_bulk_in_copy_to_guest(USBCCIDState *s, USBPacket *p)
 {
     int ret = 0;
 
-    assert(len > 0);
+    assert(p->iov.size > 0);
     ccid_bulk_in_get(s);
     if (s->current_bulk_in != NULL) {
-        ret = MIN(s->current_bulk_in->len - s->current_bulk_in->pos, len);
-        memcpy(data, s->current_bulk_in->data + s->current_bulk_in->pos, ret);
+        ret = MIN(s->current_bulk_in->len - s->current_bulk_in->pos,
+                  p->iov.size);
+        usb_packet_copy(p, s->current_bulk_in->data +
+                        s->current_bulk_in->pos, ret);
         s->current_bulk_in->pos += ret;
         if (s->current_bulk_in->pos == s->current_bulk_in->len) {
             ccid_bulk_in_release(s);
@@ -1025,11 +1027,13 @@ static int ccid_bulk_in_copy_to_guest(USBCCIDState *s, uint8_t *data, int len)
     }
     if (ret > 0) {
         DPRINTF(s, D_MORE_INFO,
-                "%s: %d/%d req/act to guest (BULK_IN)\n", __func__, len, ret);
+                "%s: %zd/%d req/act to guest (BULK_IN)\n",
+                __func__, p->iov.size, ret);
     }
-    if (ret != USB_RET_NAK && ret < len) {
+    if (ret != USB_RET_NAK && ret < p->iov.size) {
         DPRINTF(s, 1,
-            "%s: returning short (EREMOTEIO) %d < %d\n", __func__, ret, len);
+                "%s: returning short (EREMOTEIO) %d < %zd\n",
+                __func__, ret, p->iov.size);
     }
     return ret;
 }
@@ -1038,8 +1042,7 @@ static int ccid_handle_data(USBDevice *dev, USBPacket *p)
 {
     USBCCIDState *s = DO_UPCAST(USBCCIDState, dev, dev);
     int ret = 0;
-    uint8_t *data = p->data;
-    int len = p->len;
+    uint8_t buf[2];
 
     switch (p->pid) {
     case USB_TOKEN_OUT:
@@ -1049,24 +1052,25 @@ static int ccid_handle_data(USBDevice *dev, USBPacket *p)
     case USB_TOKEN_IN:
         switch (p->devep & 0xf) {
         case CCID_BULK_IN_EP:
-            if (!len) {
+            if (!p->iov.size) {
                 ret = USB_RET_NAK;
             } else {
-                ret = ccid_bulk_in_copy_to_guest(s, data, len);
+                ret = ccid_bulk_in_copy_to_guest(s, p);
             }
             break;
         case CCID_INT_IN_EP:
             if (s->notify_slot_change) {
                 /* page 56, RDR_to_PC_NotifySlotChange */
-                data[0] = CCID_MESSAGE_TYPE_RDR_to_PC_NotifySlotChange;
-                data[1] = s->bmSlotICCState;
+                buf[0] = CCID_MESSAGE_TYPE_RDR_to_PC_NotifySlotChange;
+                buf[1] = s->bmSlotICCState;
+                usb_packet_copy(p, buf, 2);
                 ret = 2;
                 s->notify_slot_change = false;
                 s->bmSlotICCState &= ~SLOT_0_CHANGED_MASK;
                 DPRINTF(s, D_INFO,
                         "handle_data: int_in: notify_slot_change %X, "
-                        "requested len %d\n",
-                        s->bmSlotICCState, len);
+                        "requested len %zd\n",
+                        s->bmSlotICCState, p->iov.size);
             }
             break;
         default:
diff --git a/hw/usb-ehci.c b/hw/usb-ehci.c
index 8b0dcc3..799e31a 100644
--- a/hw/usb-ehci.c
+++ b/hw/usb-ehci.c
@@ -1235,7 +1235,7 @@ static void ehci_async_complete_packet(USBPort *port, USBPacket *packet)
     trace_usb_ehci_queue_action(q, "wakeup");
     assert(q->async == EHCI_ASYNC_INFLIGHT);
     q->async = EHCI_ASYNC_FINISHED;
-    q->usb_status = packet->len;
+    q->usb_status = packet->result;
 }
 
 static void ehci_execute_complete(EHCIQueue *q)
@@ -1367,17 +1367,15 @@ static int ehci_execute(EHCIQueue *q)
             continue;
         }
 
-        q->packet.pid = q->pid;
-        q->packet.devaddr = devadr;
-        q->packet.devep = endp;
-        q->packet.data = q->buffer;
-        q->packet.len = q->tbytes;
+        usb_packet_setup(&q->packet, q->pid, devadr, endp);
+        usb_packet_addbuf(&q->packet, q->buffer, q->tbytes);
 
         ret = usb_handle_packet(dev, &q->packet);
 
-        DPRINTF("submit: qh %x next %x qtd %x pid %x len %d (total %d) endp %x ret %d\n",
+        DPRINTF("submit: qh %x next %x qtd %x pid %x len %zd "
+                "(total %d) endp %x ret %d\n",
                 q->qhaddr, q->qh.next, q->qtdaddr, q->pid,
-                q->packet.len, q->tbytes, endp, ret);
+                q->packet.iov.size, q->tbytes, endp, ret);
 
         if (ret != USB_RET_NODEV) {
             break;
@@ -1457,11 +1455,8 @@ static int ehci_process_itd(EHCIState *ehci,
                     continue;
                 }
 
-                ehci->ipacket.pid = pid;
-                ehci->ipacket.devaddr = devaddr;
-                ehci->ipacket.devep = endp;
-                ehci->ipacket.data = ehci->ibuffer;
-                ehci->ipacket.len = len;
+                usb_packet_setup(&ehci->ipacket, pid, devaddr, endp);
+                usb_packet_addbuf(&ehci->ipacket, ehci->ibuffer, len);
 
                 ret = usb_handle_packet(dev, &ehci->ipacket);
 
diff --git a/hw/usb-hid.c b/hw/usb-hid.c
index 9008320..541644a 100644
--- a/hw/usb-hid.c
+++ b/hw/usb-hid.c
@@ -816,6 +816,7 @@ static int usb_hid_handle_control(USBDevice *dev, USBPacket *p,
 static int usb_hid_handle_data(USBDevice *dev, USBPacket *p)
 {
     USBHIDState *s = (USBHIDState *)dev;
+    uint8_t buf[p->iov.size];
     int ret = 0;
 
     switch(p->pid) {
@@ -826,11 +827,12 @@ static int usb_hid_handle_data(USBDevice *dev, USBPacket *p)
                 return USB_RET_NAK;
             usb_hid_set_next_idle(s, curtime);
             if (s->kind == USB_MOUSE || s->kind == USB_TABLET) {
-                ret = usb_pointer_poll(s, p->data, p->len);
+                ret = usb_pointer_poll(s, buf, p->iov.size);
             }
             else if (s->kind == USB_KEYBOARD) {
-                ret = usb_keyboard_poll(s, p->data, p->len);
+                ret = usb_keyboard_poll(s, buf, p->iov.size);
             }
+            usb_packet_copy(p, buf, ret);
             s->changed = s->n > 0;
         } else {
             goto fail;
diff --git a/hw/usb-hub.c b/hw/usb-hub.c
index b49a2fe..c49c547 100644
--- a/hw/usb-hub.c
+++ b/hw/usb-hub.c
@@ -394,11 +394,12 @@ static int usb_hub_handle_data(USBDevice *dev, USBPacket *p)
         if (p->devep == 1) {
             USBHubPort *port;
             unsigned int status;
+            uint8_t buf[4];
             int i, n;
             n = (NUM_PORTS + 1 + 7) / 8;
-            if (p->len == 1) { /* FreeBSD workaround */
+            if (p->iov.size == 1) { /* FreeBSD workaround */
                 n = 1;
-            } else if (n > p->len) {
+            } else if (n > p->iov.size) {
                 return USB_RET_BABBLE;
             }
             status = 0;
@@ -409,8 +410,9 @@ static int usb_hub_handle_data(USBDevice *dev, USBPacket *p)
             }
             if (status != 0) {
                 for(i = 0; i < n; i++) {
-                    p->data[i] = status >> (8 * i);
+                    buf[i] = status >> (8 * i);
                 }
+                usb_packet_copy(p, buf, n);
                 ret = n;
             } else {
                 ret = USB_RET_NAK; /* usb11 11.13.1 */
diff --git a/hw/usb-libhw.c b/hw/usb-libhw.c
new file mode 100644
index 0000000..162b42b
--- /dev/null
+++ b/hw/usb-libhw.c
@@ -0,0 +1,63 @@
+/*
+ * QEMU USB emulation, libhw bits.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include "qemu-common.h"
+#include "cpu-common.h"
+#include "usb.h"
+#include "dma.h"
+
+int usb_packet_map(USBPacket *p, QEMUSGList *sgl)
+{
+    int is_write = (p->pid == USB_TOKEN_IN);
+    target_phys_addr_t len;
+    void *mem;
+    int i;
+
+    for (i = 0; i < sgl->nsg; i++) {
+        len = sgl->sg[i].len;
+        mem = cpu_physical_memory_map(sgl->sg[i].base, &len,
+                                      is_write);
+        if (!mem) {
+            goto err;
+        }
+        qemu_iovec_add(&p->iov, mem, len);
+        if (len != sgl->sg[i].len) {
+            goto err;
+        }
+    }
+    return 0;
+
+err:
+    usb_packet_unmap(p);
+    return -1;
+}
+
+void usb_packet_unmap(USBPacket *p)
+{
+    int is_write = (p->pid == USB_TOKEN_IN);
+    int i;
+
+    for (i = 0; i < p->iov.niov; i++) {
+        cpu_physical_memory_unmap(p->iov.iov[i].iov_base,
+                                  p->iov.iov[i].iov_len, is_write,
+                                  p->iov.iov[i].iov_len);
+    }
+}
diff --git a/hw/usb-msd.c b/hw/usb-msd.c
index cdeac58..48e0b34 100644
--- a/hw/usb-msd.c
+++ b/hw/usb-msd.c
@@ -207,8 +207,9 @@ static void usb_msd_send_status(MSDState *s, USBPacket *p)
     csw.residue = s->residue;
     csw.status = s->result;
 
-    len = MIN(sizeof(csw), p->len);
-    memcpy(p->data, &csw, len);
+    len = MIN(sizeof(csw), p->iov.size);
+    usb_packet_copy(p, &csw, len);
+    p->result = len;
 }
 
 static void usb_msd_transfer_data(SCSIRequest *req, uint32_t len)
@@ -222,6 +223,7 @@ static void usb_msd_transfer_data(SCSIRequest *req, uint32_t len)
     if (p) {
         usb_msd_copy_data(s);
         if (s->packet && s->usb_len == 0) {
+            p->result = p->iov.size;
             /* Set s->packet to NULL before calling usb_packet_complete
                because another request may be issued before
                usb_packet_complete returns.  */
@@ -257,6 +259,7 @@ static void usb_msd_command_complete(SCSIRequest *req, uint32_t status)
             if (s->data_len == 0) {
                 s->mode = USB_MSDM_CSW;
             }
+            p->result = p->iov.size;
         }
         s->packet = NULL;
         usb_packet_complete(&s->dev, p);
@@ -342,9 +345,10 @@ static int usb_msd_handle_data(USBDevice *dev, USBPacket *p)
     int ret = 0;
     struct usb_msd_cbw cbw;
     uint8_t devep = p->devep;
-    uint8_t *data = p->data;
-    int len = p->len;
+    uint8_t *data = p->iov.iov[0].iov_base;
+    int len = p->iov.iov[0].iov_len;
 
+    assert(p->iov.niov == 1); /* temporary */
     switch (p->pid) {
     case USB_TOKEN_OUT:
         if (devep != 2)
diff --git a/hw/usb-musb.c b/hw/usb-musb.c
index 035dda8..d3ccde9 100644
--- a/hw/usb-musb.c
+++ b/hw/usb-musb.c
@@ -365,6 +365,8 @@ struct MUSBState *musb_init(qemu_irq *irqs)
         s->ep[i].maxp[1] = 0x40;
         s->ep[i].musb = s;
         s->ep[i].epnum = i;
+        usb_packet_init(&s->ep[i].packey[0].p);
+        usb_packet_init(&s->ep[i].packey[1].p);
     }
 
     usb_bus_new(&s->bus, &musb_bus_ops, NULL /* FIXME */);
@@ -605,12 +607,10 @@ static void musb_packet(MUSBState *s, MUSBEndPoint *ep,
     ep->interrupt[dir] = ttype == USB_ENDPOINT_XFER_INT;
     ep->delayed_cb[dir] = cb;
 
-    ep->packey[dir].p.pid = pid;
     /* A wild guess on the FADDR semantics... */
-    ep->packey[dir].p.devaddr = ep->faddr[idx];
-    ep->packey[dir].p.devep = ep->type[idx] & 0xf;
-    ep->packey[dir].p.data = (void *) ep->buf[idx];
-    ep->packey[dir].p.len = len;
+    usb_packet_setup(&ep->packey[dir].p, pid, ep->faddr[idx],
+                     ep->type[idx] & 0xf);
+    usb_packet_addbuf(&ep->packey[dir].p, ep->buf[idx], len);
     ep->packey[dir].ep = ep;
     ep->packey[dir].dir = dir;
 
@@ -738,7 +738,7 @@ static void musb_rx_packet_complete(USBPacket *packey, void *opaque)
 
     if (ep->status[1] == USB_RET_STALL) {
         ep->status[1] = 0;
-        packey->len = 0;
+        packey->result = 0;
 
         ep->csr[1] |= MGC_M_RXCSR_H_RXSTALL;
         if (!epnum)
@@ -752,7 +752,7 @@ static void musb_rx_packet_complete(USBPacket *packey, void *opaque)
          * Data-errors in Isochronous.  */
         if (ep->interrupt[1])
             return musb_packet(s, ep, epnum, USB_TOKEN_IN,
-                            packey->len, musb_rx_packet_complete, 1);
+                            packey->iov.size, musb_rx_packet_complete, 1);
 
         ep->csr[1] |= MGC_M_RXCSR_DATAERROR;
         if (!epnum)
@@ -777,14 +777,14 @@ static void musb_rx_packet_complete(USBPacket *packey, void *opaque)
     /* TODO: check len for over/underruns of an OUT packet?  */
     /* TODO: perhaps make use of e->ext_size[1] here.  */
 
-    packey->len = ep->status[1];
+    packey->result = ep->status[1];
 
     if (!(ep->csr[1] & (MGC_M_RXCSR_H_RXSTALL | MGC_M_RXCSR_DATAERROR))) {
         ep->csr[1] |= MGC_M_RXCSR_FIFOFULL | MGC_M_RXCSR_RXPKTRDY;
         if (!epnum)
             ep->csr[0] |= MGC_M_CSR0_RXPKTRDY;
 
-        ep->rxcount = packey->len; /* XXX: MIN(packey->len, ep->maxp[1]); */
+        ep->rxcount = packey->result; /* XXX: MIN(packey->len, ep->maxp[1]); */
         /* In DMA mode: assert DMA request for this EP */
     }
 
@@ -856,12 +856,12 @@ static void musb_rx_req(MUSBState *s, int epnum)
      * 64 bytes of the FIFO, only move the FIFO start and return. (Obsolete) */
     if (ep->packey[1].p.pid == USB_TOKEN_IN && ep->status[1] >= 0 &&
                     (ep->fifostart[1]) + ep->rxcount <
-                    ep->packey[1].p.len) {
+                    ep->packey[1].p.iov.size) {
         TRACE("0x%08x, %d",  ep->fifostart[1], ep->rxcount );
         ep->fifostart[1] += ep->rxcount;
         ep->fifolen[1] = 0;
 
-        ep->rxcount = MIN(ep->packey[0].p.len - (ep->fifostart[1]),
+        ep->rxcount = MIN(ep->packey[0].p.iov.size - (ep->fifostart[1]),
                         ep->maxp[1]);
 
         ep->csr[1] &= ~MGC_M_RXCSR_H_REQPKT;
diff --git a/hw/usb-net.c b/hw/usb-net.c
index 4212e5b..0cb47d6 100644
--- a/hw/usb-net.c
+++ b/hw/usb-net.c
@@ -29,6 +29,7 @@
 #include "net.h"
 #include "qemu-queue.h"
 #include "sysemu.h"
+#include "iov.h"
 
 /*#define TRAFFIC_DEBUG*/
 /* Thanks to NetChip Technologies for donating this product ID.
@@ -1121,28 +1122,23 @@ static int usb_net_handle_control(USBDevice *dev, USBPacket *p,
 
 static int usb_net_handle_statusin(USBNetState *s, USBPacket *p)
 {
+    le32 buf[2];
     int ret = 8;
 
-    if (p->len < 8)
+    if (p->iov.size < 8) {
         return USB_RET_STALL;
+    }
 
-    ((le32 *) p->data)[0] = cpu_to_le32(1);
-    ((le32 *) p->data)[1] = cpu_to_le32(0);
+    buf[0] = cpu_to_le32(1);
+    buf[1] = cpu_to_le32(0);
+    usb_packet_copy(p, buf, 8);
     if (!s->rndis_resp.tqh_first)
         ret = USB_RET_NAK;
 
 #ifdef TRAFFIC_DEBUG
-    fprintf(stderr, "usbnet: interrupt poll len %u return %d", p->len, ret);
-    {
-        int i;
-        fprintf(stderr, ":");
-        for (i = 0; i < ret; i++) {
-            if (!(i & 15))
-                fprintf(stderr, "\n%04x:", i);
-            fprintf(stderr, " %02x", p->data[i]);
-        }
-        fprintf(stderr, "\n\n");
-    }
+    fprintf(stderr, "usbnet: interrupt poll len %zu return %d",
+            p->iov.size, ret);
+    iov_hexdump(p->iov.iov, p->iov.niov, stderr, "usbnet", ret);
 #endif
 
     return ret;
@@ -1162,9 +1158,10 @@ static int usb_net_handle_datain(USBNetState *s, USBPacket *p)
         return ret;
     }
     ret = s->in_len - s->in_ptr;
-    if (ret > p->len)
-        ret = p->len;
-    memcpy(p->data, &s->in_buf[s->in_ptr], ret);
+    if (ret > p->iov.size) {
+        ret = p->iov.size;
+    }
+    usb_packet_copy(p, &s->in_buf[s->in_ptr], ret);
     s->in_ptr += ret;
     if (s->in_ptr >= s->in_len &&
                     (is_rndis(s) || (s->in_len & (64 - 1)) || !ret)) {
@@ -1173,17 +1170,8 @@ static int usb_net_handle_datain(USBNetState *s, USBPacket *p)
     }
 
 #ifdef TRAFFIC_DEBUG
-    fprintf(stderr, "usbnet: data in len %u return %d", p->len, ret);
-    {
-        int i;
-        fprintf(stderr, ":");
-        for (i = 0; i < ret; i++) {
-            if (!(i & 15))
-                fprintf(stderr, "\n%04x:", i);
-            fprintf(stderr, " %02x", p->data[i]);
-        }
-        fprintf(stderr, "\n\n");
-    }
+    fprintf(stderr, "usbnet: data in len %zu return %d", p->iov.size, ret);
+    iov_hexdump(p->iov.iov, p->iov.niov, stderr, "usbnet", ret);
 #endif
 
     return ret;
@@ -1191,29 +1179,20 @@ static int usb_net_handle_datain(USBNetState *s, USBPacket *p)
 
 static int usb_net_handle_dataout(USBNetState *s, USBPacket *p)
 {
-    int ret = p->len;
+    int ret = p->iov.size;
     int sz = sizeof(s->out_buf) - s->out_ptr;
     struct rndis_packet_msg_type *msg =
             (struct rndis_packet_msg_type *) s->out_buf;
     uint32_t len;
 
 #ifdef TRAFFIC_DEBUG
-    fprintf(stderr, "usbnet: data out len %u\n", p->len);
-    {
-        int i;
-        fprintf(stderr, ":");
-        for (i = 0; i < p->len; i++) {
-            if (!(i & 15))
-                fprintf(stderr, "\n%04x:", i);
-            fprintf(stderr, " %02x", p->data[i]);
-        }
-        fprintf(stderr, "\n\n");
-    }
+    fprintf(stderr, "usbnet: data out len %zu\n", p->iov.size);
+    iov_hexdump(p->iov.iov, p->iov.niov, stderr, "usbnet", p->iov.size);
 #endif
 
     if (sz > ret)
         sz = ret;
-    memcpy(&s->out_buf[s->out_ptr], p->data, sz);
+    usb_packet_copy(p, &s->out_buf[s->out_ptr], sz);
     s->out_ptr += sz;
 
     if (!is_rndis(s)) {
@@ -1277,8 +1256,8 @@ static int usb_net_handle_data(USBDevice *dev, USBPacket *p)
     }
     if (ret == USB_RET_STALL)
         fprintf(stderr, "usbnet: failed data transaction: "
-                        "pid 0x%x ep 0x%x len 0x%x\n",
-                        p->pid, p->devep, p->len);
+                        "pid 0x%x ep 0x%x len 0x%zx\n",
+                        p->pid, p->devep, p->iov.size);
     return ret;
 }
 
diff --git a/hw/usb-ohci.c b/hw/usb-ohci.c
index 337b250..d39bcb0 100644
--- a/hw/usb-ohci.c
+++ b/hw/usb-ohci.c
@@ -777,18 +777,17 @@ static int ohci_service_iso_td(OHCIState *ohci, struct ohci_ed *ed,
     }
 
     if (completion) {
-        ret = ohci->usb_packet.len;
+        ret = ohci->usb_packet.result;
     } else {
         ret = USB_RET_NODEV;
         for (i = 0; i < ohci->num_ports; i++) {
             dev = ohci->rhport[i].port.dev;
             if ((ohci->rhport[i].ctrl & OHCI_PORT_PES) == 0)
                 continue;
-            ohci->usb_packet.pid = pid;
-            ohci->usb_packet.devaddr = OHCI_BM(ed->flags, ED_FA);
-            ohci->usb_packet.devep = OHCI_BM(ed->flags, ED_EN);
-            ohci->usb_packet.data = ohci->usb_buf;
-            ohci->usb_packet.len = len;
+            usb_packet_setup(&ohci->usb_packet, pid,
+                             OHCI_BM(ed->flags, ED_FA),
+                             OHCI_BM(ed->flags, ED_EN));
+            usb_packet_addbuf(&ohci->usb_packet, ohci->usb_buf, len);
             ret = usb_handle_packet(dev, &ohci->usb_packet);
             if (ret != USB_RET_NODEV)
                 break;
@@ -959,7 +958,7 @@ static int ohci_service_td(OHCIState *ohci, struct ohci_ed *ed)
     }
 #endif
     if (completion) {
-        ret = ohci->usb_packet.len;
+        ret = ohci->usb_packet.result;
         ohci->async_td = 0;
         ohci->async_complete = 0;
     } else {
@@ -980,11 +979,10 @@ static int ohci_service_td(OHCIState *ohci, struct ohci_ed *ed)
 #endif
                 return 1;
             }
-            ohci->usb_packet.pid = pid;
-            ohci->usb_packet.devaddr = OHCI_BM(ed->flags, ED_FA);
-            ohci->usb_packet.devep = OHCI_BM(ed->flags, ED_EN);
-            ohci->usb_packet.data = ohci->usb_buf;
-            ohci->usb_packet.len = len;
+            usb_packet_setup(&ohci->usb_packet, pid,
+                             OHCI_BM(ed->flags, ED_FA),
+                             OHCI_BM(ed->flags, ED_EN));
+            usb_packet_addbuf(&ohci->usb_packet, ohci->usb_buf, len);
             ret = usb_handle_packet(dev, &ohci->usb_packet);
             if (ret != USB_RET_NODEV)
                 break;
@@ -1761,6 +1759,7 @@ static int usb_ohci_init(OHCIState *ohci, DeviceState *dev,
     ohci->localmem_base = localmem_base;
 
     ohci->name = dev->info->name;
+    usb_packet_init(&ohci->usb_packet);
 
     ohci->async_td = 0;
     qemu_register_reset(ohci_reset, ohci);
diff --git a/hw/usb-serial.c b/hw/usb-serial.c
index 298c1e9..09731da 100644
--- a/hw/usb-serial.c
+++ b/hw/usb-serial.c
@@ -361,10 +361,11 @@ static int usb_serial_handle_data(USBDevice *dev, USBPacket *p)
     USBSerialState *s = (USBSerialState *)dev;
     int ret = 0;
     uint8_t devep = p->devep;
-    uint8_t *data = p->data;
-    int len = p->len;
+    uint8_t *data = p->iov.iov[0].iov_base;
+    int len = p->iov.iov[0].iov_len;
     int first_len;
 
+    assert(p->iov.niov == 1); /* temporary */
     switch (p->pid) {
     case USB_TOKEN_OUT:
         if (devep != 2)
diff --git a/hw/usb-uhci.c b/hw/usb-uhci.c
index da74c57..20b829b 100644
--- a/hw/usb-uhci.c
+++ b/hw/usb-uhci.c
@@ -30,6 +30,7 @@
 #include "pci.h"
 #include "qemu-timer.h"
 #include "usb-uhci.h"
+#include "iov.h"
 
 //#define DEBUG
 //#define DEBUG_DUMP_DATA
@@ -93,17 +94,12 @@ static const char *pid2str(int pid)
 #endif
 
 #ifdef DEBUG_DUMP_DATA
-static void dump_data(const uint8_t *data, int len)
+static void dump_data(USBPacket *p, int ret)
 {
-    int i;
-
-    printf("uhci: data: ");
-    for(i = 0; i < len; i++)
-        printf(" %02x", data[i]);
-    printf("\n");
+    iov_hexdump(p->iov.iov, p->iov.niov, stderr, "uhci", ret);
 }
 #else
-static void dump_data(const uint8_t *data, int len) {}
+static void dump_data(USBPacket *p, int ret) {}
 #endif
 
 typedef struct UHCIState UHCIState;
@@ -179,12 +175,14 @@ static UHCIAsync *uhci_async_alloc(UHCIState *s)
     async->token = 0;
     async->done  = 0;
     async->isoc  = 0;
+    usb_packet_init(&async->packet);
 
     return async;
 }
 
 static void uhci_async_free(UHCIState *s, UHCIAsync *async)
 {
+    usb_packet_cleanup(&async->packet);
     qemu_free(async);
 }
 
@@ -648,10 +646,10 @@ static int uhci_broadcast_packet(UHCIState *s, USBPacket *p)
 {
     int i, ret;
 
-    DPRINTF("uhci: packet enter. pid %s addr 0x%02x ep %d len %d\n",
-           pid2str(p->pid), p->devaddr, p->devep, p->len);
+    DPRINTF("uhci: packet enter. pid %s addr 0x%02x ep %d len %zd\n",
+           pid2str(p->pid), p->devaddr, p->devep, p->iov.size);
     if (p->pid == USB_TOKEN_OUT || p->pid == USB_TOKEN_SETUP)
-        dump_data(p->data, p->len);
+        dump_data(p, 0);
 
     ret = USB_RET_NODEV;
     for (i = 0; i < NB_PORTS && ret == USB_RET_NODEV; i++) {
@@ -662,9 +660,9 @@ static int uhci_broadcast_packet(UHCIState *s, USBPacket *p)
             ret = usb_handle_packet(dev, p);
     }
 
-    DPRINTF("uhci: packet exit. ret %d len %d\n", ret, p->len);
+    DPRINTF("uhci: packet exit. ret %d len %zd\n", ret, p->iov.size);
     if (p->pid == USB_TOKEN_IN && ret > 0)
-        dump_data(p->data, ret);
+        dump_data(p, ret);
 
     return ret;
 }
@@ -684,7 +682,7 @@ static int uhci_complete_td(UHCIState *s, UHCI_TD *td, UHCIAsync *async, uint32_
     max_len = ((td->token >> 21) + 1) & 0x7ff;
     pid = td->token & 0xff;
 
-    ret = async->packet.len;
+    ret = async->packet.result;
 
     if (td->ctrl & TD_CTRL_IOS)
         td->ctrl &= ~TD_CTRL_ACTIVE;
@@ -692,7 +690,7 @@ static int uhci_complete_td(UHCIState *s, UHCI_TD *td, UHCIAsync *async, uint32_
     if (ret < 0)
         goto out;
 
-    len = async->packet.len;
+    len = async->packet.result;
     td->ctrl = (td->ctrl & ~0x7ff) | ((len - 1) & 0x7ff);
 
     /* The NAK bit may have been set by a previous frame, so clear it
@@ -827,11 +825,9 @@ static int uhci_handle_td(UHCIState *s, uint32_t addr, UHCI_TD *td, uint32_t *in
     max_len = ((td->token >> 21) + 1) & 0x7ff;
     pid = td->token & 0xff;
 
-    async->packet.pid     = pid;
-    async->packet.devaddr = (td->token >> 8) & 0x7f;
-    async->packet.devep   = (td->token >> 15) & 0xf;
-    async->packet.data    = async->buffer;
-    async->packet.len     = max_len;
+    usb_packet_setup(&async->packet, pid, (td->token >> 8) & 0x7f,
+                     (td->token >> 15) & 0xf);
+    usb_packet_addbuf(&async->packet, async->buffer, max_len);
 
     switch(pid) {
     case USB_TOKEN_OUT:
@@ -859,7 +855,7 @@ static int uhci_handle_td(UHCIState *s, uint32_t addr, UHCI_TD *td, uint32_t *in
         return 2;
     }
 
-    async->packet.len = len;
+    async->packet.result = len;
 
 done:
     len = uhci_complete_td(s, td, async, int_mask);
diff --git a/hw/usb-wacom.c b/hw/usb-wacom.c
index d76ee97..2558006 100644
--- a/hw/usb-wacom.c
+++ b/hw/usb-wacom.c
@@ -308,6 +308,7 @@ static int usb_wacom_handle_control(USBDevice *dev, USBPacket *p,
 static int usb_wacom_handle_data(USBDevice *dev, USBPacket *p)
 {
     USBWacomState *s = (USBWacomState *) dev;
+    uint8_t buf[p->iov.size];
     int ret = 0;
 
     switch (p->pid) {
@@ -317,9 +318,10 @@ static int usb_wacom_handle_data(USBDevice *dev, USBPacket *p)
                 return USB_RET_NAK;
             s->changed = 0;
             if (s->mode == WACOM_MODE_HID)
-                ret = usb_mouse_poll(s, p->data, p->len);
+                ret = usb_mouse_poll(s, buf, p->iov.size);
             else if (s->mode == WACOM_MODE_WACOM)
-                ret = usb_wacom_poll(s, p->data, p->len);
+                ret = usb_wacom_poll(s, buf, p->iov.size);
+            usb_packet_copy(p, buf, ret);
             break;
         }
         /* Fall through.  */
diff --git a/hw/usb.c b/hw/usb.c
index 27a983c..685e775 100644
--- a/hw/usb.c
+++ b/hw/usb.c
@@ -25,6 +25,7 @@
  */
 #include "qemu-common.h"
 #include "usb.h"
+#include "iov.h"
 
 void usb_attach(USBPort *port, USBDevice *dev)
 {
@@ -72,10 +73,11 @@ static int do_token_setup(USBDevice *s, USBPacket *p)
     int request, value, index;
     int ret = 0;
 
-    if (p->len != 8)
+    if (p->iov.size != 8) {
         return USB_RET_STALL;
- 
-    memcpy(s->setup_buf, p->data, 8);
+    }
+
+    usb_packet_copy(p, s->setup_buf, p->iov.size);
     s->setup_len   = (s->setup_buf[7] << 8) | s->setup_buf[6];
     s->setup_index = 0;
 
@@ -144,9 +146,10 @@ static int do_token_in(USBDevice *s, USBPacket *p)
     case SETUP_STATE_DATA:
         if (s->setup_buf[0] & USB_DIR_IN) {
             int len = s->setup_len - s->setup_index;
-            if (len > p->len)
-                len = p->len;
-            memcpy(p->data, s->data_buf + s->setup_index, len);
+            if (len > p->iov.size) {
+                len = p->iov.size;
+            }
+            usb_packet_copy(p, s->data_buf + s->setup_index, len);
             s->setup_index += len;
             if (s->setup_index >= s->setup_len)
                 s->setup_state = SETUP_STATE_ACK;
@@ -179,9 +182,10 @@ static int do_token_out(USBDevice *s, USBPacket *p)
     case SETUP_STATE_DATA:
         if (!(s->setup_buf[0] & USB_DIR_IN)) {
             int len = s->setup_len - s->setup_index;
-            if (len > p->len)
-                len = p->len;
-            memcpy(s->data_buf + s->setup_index, p->data, len);
+            if (len > p->iov.size) {
+                len = p->iov.size;
+            }
+            usb_packet_copy(p, s->data_buf + s->setup_index, len);
             s->setup_index += len;
             if (s->setup_index >= s->setup_len)
                 s->setup_state = SETUP_STATE_ACK;
@@ -251,22 +255,22 @@ int usb_generic_handle_packet(USBDevice *s, USBPacket *p)
    usb_packet_complete to complete their async control packets. */
 void usb_generic_async_ctrl_complete(USBDevice *s, USBPacket *p)
 {
-    if (p->len < 0) {
+    if (p->result < 0) {
         s->setup_state = SETUP_STATE_IDLE;
     }
 
     switch (s->setup_state) {
     case SETUP_STATE_SETUP:
-        if (p->len < s->setup_len) {
-            s->setup_len = p->len;
+        if (p->result < s->setup_len) {
+            s->setup_len = p->result;
         }
         s->setup_state = SETUP_STATE_DATA;
-        p->len = 8;
+        p->result = 8;
         break;
 
     case SETUP_STATE_ACK:
         s->setup_state = SETUP_STATE_IDLE;
-        p->len = 0;
+        p->result = 0;
         break;
 
     default:
@@ -347,3 +351,57 @@ void usb_cancel_packet(USBPacket * p)
     p->owner->info->cancel_packet(p->owner, p);
     p->owner = NULL;
 }
+
+
+void usb_packet_init(USBPacket *p)
+{
+    qemu_iovec_init(&p->iov, 1);
+}
+
+void usb_packet_setup(USBPacket *p, int pid, uint8_t addr, uint8_t ep)
+{
+    p->pid = pid;
+    p->devaddr = addr;
+    p->devep = ep;
+    p->result = 0;
+    qemu_iovec_reset(&p->iov);
+}
+
+void usb_packet_addbuf(USBPacket *p, void *ptr, size_t len)
+{
+    qemu_iovec_add(&p->iov, ptr, len);
+}
+
+void usb_packet_copy(USBPacket *p, void *ptr, size_t bytes)
+{
+    assert(p->result >= 0);
+    assert(p->result + bytes <= p->iov.size);
+    switch (p->pid) {
+    case USB_TOKEN_SETUP:
+    case USB_TOKEN_OUT:
+        iov_to_buf(p->iov.iov, p->iov.niov, ptr, p->result, bytes);
+        break;
+    case USB_TOKEN_IN:
+        iov_from_buf(p->iov.iov, p->iov.niov, ptr, p->result, bytes);
+        break;
+    default:
+        fprintf(stderr, "%s: invalid pid: %x\n", __func__, p->pid);
+        abort();
+    }
+    p->result += bytes;
+}
+
+void usb_packet_skip(USBPacket *p, size_t bytes)
+{
+    assert(p->result >= 0);
+    assert(p->result + bytes <= p->iov.size);
+    if (p->pid == USB_TOKEN_IN) {
+        iov_clear(p->iov.iov, p->iov.niov, p->result, bytes);
+    }
+    p->result += bytes;
+}
+
+void usb_packet_cleanup(USBPacket *p)
+{
+    qemu_iovec_destroy(&p->iov);
+}
diff --git a/hw/usb.h b/hw/usb.h
index ded2de2..84d04df 100644
--- a/hw/usb.h
+++ b/hw/usb.h
@@ -285,12 +285,21 @@ struct USBPacket {
     int pid;
     uint8_t devaddr;
     uint8_t devep;
-    uint8_t *data;
-    int len;
+    QEMUIOVector iov;
+    int result; /* transfer length or USB_RET_* status code */
     /* Internal use by the USB layer.  */
     USBDevice *owner;
 };
 
+void usb_packet_init(USBPacket *p);
+void usb_packet_setup(USBPacket *p, int pid, uint8_t addr, uint8_t ep);
+void usb_packet_addbuf(USBPacket *p, void *ptr, size_t len);
+int usb_packet_map(USBPacket *p, QEMUSGList *sgl);
+void usb_packet_unmap(USBPacket *p);
+void usb_packet_copy(USBPacket *p, void *ptr, size_t bytes);
+void usb_packet_skip(USBPacket *p, size_t bytes);
+void usb_packet_cleanup(USBPacket *p);
+
 int usb_handle_packet(USBDevice *dev, USBPacket *p);
 void usb_packet_complete(USBDevice *dev, USBPacket *p);
 void usb_cancel_packet(USBPacket * p);