usb: add short-packet handling to usb-storage driver

The dwc-hsotg (dwc2) USB host depends on a short packet to
indicate the end of an IN transfer. The usb-storage driver
currently doesn't provide this, so fix it.

I have tested this change rather extensively using a PC
emulation with xhci, ehci, and uhci controllers, and have
not observed any regressions.
Signed-off-by: NPaul Zimmerman <pauldzim@gmail.com>
Message-id: 20200520235349.21215-6-pauldzim@gmail.com
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

hw/usb/dev-storage.c

@@ -229,6 +229,9 @@ static void usb_msd_copy_data(MSDState *s, USBPacket *p)
     usb_packet_copy(p, scsi_req_get_buf(s->req) + s->scsi_off, len);
     s->scsi_len -= len;
     s->scsi_off += len;
+    if (len > s->data_len) {
+        len = s->data_len;
+    }
     s->data_len -= len;
     if (s->scsi_len == 0 || s->data_len == 0) {
         scsi_req_continue(s->req);
@@ -303,6 +306,9 @@ static void usb_msd_command_complete(SCSIRequest *req, uint32_t status, size_t r
             if (s->data_len) {
                 int len = (p->iov.size - p->actual_length);
                 usb_packet_skip(p, len);
+                if (len > s->data_len) {
+                    len = s->data_len;
+                }
                 s->data_len -= len;
             }
             if (s->data_len == 0) {
@@ -469,6 +475,9 @@ static void usb_msd_handle_data(USBDevice *dev, USBPacket *p)
                 int len = p->iov.size - p->actual_length;
                 if (len) {
                     usb_packet_skip(p, len);
+                    if (len > s->data_len) {
+                        len = s->data_len;
+                    }
                     s->data_len -= len;
                     if (s->data_len == 0) {
                         s->mode = USB_MSDM_CSW;
@@ -528,13 +537,17 @@ static void usb_msd_handle_data(USBDevice *dev, USBPacket *p)
                 int len = p->iov.size - p->actual_length;
                 if (len) {
                     usb_packet_skip(p, len);
+                    if (len > s->data_len) {
+                        len = s->data_len;
+                    }
                     s->data_len -= len;
                     if (s->data_len == 0) {
                         s->mode = USB_MSDM_CSW;
                     }
                 }
             }
-            if (p->actual_length < p->iov.size) {
+            if (p->actual_length < p->iov.size && (p->short_not_ok ||
+                    s->scsi_len >= p->ep->max_packet_size)) {
                 DPRINTF("Deferring packet %p [wait data-in]\n", p);
                 s->packet = p;
                 p->status = USB_RET_ASYNC;