uhci: Use an intermediate buffer for usb packet data

Due to various unfortunate reasons we cannot reliable detect a guest
cancelling a packet as soon as it happens, instead we detect cancels
with some delay.

When packets are handled async, and we directly pass the guest memory for
the packet to the usb-device as iovec, this means that the usb-device can
write to guest-memory which the guest has already re-used for other purposes
-> not good!

This patch fixes this by adding an intermediate buffer and writing back not
only the result, but also the data, of async completed packets when scanning
the schedule.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/usb/hcd-uhci.c

@@ -119,7 +119,8 @@ struct UHCIPCIDeviceClass {
 
 struct UHCIAsync {
     USBPacket packet;
-    QEMUSGList sgl;
+    uint8_t   static_buf[64]; /* 64 bytes is enough, except for isoc packets */
+    uint8_t   *buf;
     UHCIQueue *queue;
     QTAILQ_ENTRY(UHCIAsync) next;
     uint32_t  td_addr;
@@ -264,7 +265,6 @@ static UHCIAsync *uhci_async_alloc(UHCIQueue *queue, uint32_t td_addr)
     async->queue = queue;
     async->td_addr = td_addr;
     usb_packet_init(&async->packet);
-    pci_dma_sglist_init(&async->sgl, &queue->uhci->dev, 1);
     trace_usb_uhci_packet_add(async->queue->token, async->td_addr);
 
     return async;
@@ -274,7 +274,9 @@ static void uhci_async_free(UHCIAsync *async)
 {
     trace_usb_uhci_packet_del(async->queue->token, async->td_addr);
     usb_packet_cleanup(&async->packet);
-    qemu_sglist_destroy(&async->sgl);
+    if (async->buf != async->static_buf) {
+        g_free(async->buf);
+    }
     g_free(async);
 }
 
@@ -299,7 +301,6 @@ static void uhci_async_cancel(UHCIAsync *async)
                                  async->done);
     if (!async->done)
         usb_cancel_packet(&async->packet);
-    usb_packet_unmap(&async->packet, &async->sgl);
     uhci_async_free(async);
 }
 
@@ -774,6 +775,7 @@ static int uhci_complete_td(UHCIState *s, UHCI_TD *td, UHCIAsync *async, uint32_
         *int_mask |= 0x01;
 
     if (pid == USB_TOKEN_IN) {
+        pci_dma_write(&s->dev, td->buffer, async->buf, len);
         if ((td->ctrl & TD_CTRL_SPD) && len < max_len) {
             *int_mask |= 0x02;
             /* short packet: do not update QH */
@@ -881,12 +883,17 @@ static int uhci_handle_td(UHCIState *s, UHCIQueue *q, uint32_t qh_addr,
     spd = (pid == USB_TOKEN_IN && (td->ctrl & TD_CTRL_SPD) != 0);
     usb_packet_setup(&async->packet, pid, q->ep, 0, td_addr, spd,
                      (td->ctrl & TD_CTRL_IOC) != 0);
-    qemu_sglist_add(&async->sgl, td->buffer, max_len);
-    usb_packet_map(&async->packet, &async->sgl);
+    if (max_len <= sizeof(async->static_buf)) {
+        async->buf = async->static_buf;
+    } else {
+        async->buf = g_malloc(max_len);
+    }
+    usb_packet_addbuf(&async->packet, async->buf, max_len);
 
     switch(pid) {
     case USB_TOKEN_OUT:
     case USB_TOKEN_SETUP:
+        pci_dma_read(&s->dev, td->buffer, async->buf, max_len);
         usb_handle_packet(q->ep->dev, &async->packet);
         if (async->packet.status == USB_RET_SUCCESS) {
             async->packet.actual_length = max_len;
@@ -899,7 +906,6 @@ static int uhci_handle_td(UHCIState *s, UHCIQueue *q, uint32_t qh_addr,
 
     default:
         /* invalid pid : frame interrupted */
-        usb_packet_unmap(&async->packet, &async->sgl);
         uhci_async_free(async);
         s->status |= UHCI_STS_HCPERR;
         uhci_update_irq(s);
@@ -916,7 +922,6 @@ static int uhci_handle_td(UHCIState *s, UHCIQueue *q, uint32_t qh_addr,
 
 done:
     ret = uhci_complete_td(s, td, async, int_mask);
-    usb_packet_unmap(&async->packet, &async->sgl);
     uhci_async_free(async);
     return ret;
 }