hw/xen: Pass grant ref to gnttab unmap operation

The previous commit introduced redirectable gnttab operations fairly
much like-for-like, with the exception of the extra arguments to the
->open() call which were always NULL/0 anyway.

This *changes* the arguments to the ->unmap() operation to include the
original ref# that was mapped. Under real Xen it isn't necessary; all we
need to do from QEMU is munmap(), then the kernel will release the grant,
and Xen does the tracking/refcounting for the guest.

When we have emulated grant tables though, we need to do all that for
ourselves. So let's have the back ends keep track of what they mapped
and pass it in to the ->unmap() method for us.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>

1 files changed, 16 insertions, 5 deletions

diff --git a/hw/usb/xen-usb.c b/hw/usb/xen-usb.c
index 0f7369e..a770a64 100644
--- a/hw/usb/xen-usb.c
+++ b/hw/usb/xen-usb.c
@@ -101,6 +101,8 @@ struct usbback_hotplug {
 struct usbback_info {
     struct XenLegacyDevice         xendev;  /* must be first */
     USBBus                   bus;
+    uint32_t                 urb_ring_ref;
+    uint32_t                 conn_ring_ref;
     void                     *urb_sring;
     void                     *conn_sring;
     struct usbif_urb_back_ring urb_ring;
@@ -277,10 +279,11 @@ static int usbback_init_packet(struct usbback_req *usbback_req)
 static void usbback_do_response(struct usbback_req *usbback_req, int32_t status,
                                 int32_t actual_length, int32_t error_count)
 {
+    uint32_t ref[USBIF_MAX_SEGMENTS_PER_REQUEST];
     struct usbback_info *usbif;
     struct usbif_urb_response *res;
     struct XenLegacyDevice *xendev;
-    unsigned int notify;
+    unsigned int notify, i;
 
     usbif = usbback_req->usbif;
     xendev = &usbif->xendev;
@@ -293,13 +296,19 @@ static void usbback_do_response(struct usbback_req *usbback_req, int32_t status,
     }
 
     if (usbback_req->buffer) {
-        xen_be_unmap_grant_refs(xendev, usbback_req->buffer,
+        for (i = 0; i < usbback_req->nr_buffer_segs; i++) {
+            ref[i] = usbback_req->req.seg[i].gref;
+        }
+        xen_be_unmap_grant_refs(xendev, usbback_req->buffer, ref,
                                 usbback_req->nr_buffer_segs);
         usbback_req->buffer = NULL;
     }
 
     if (usbback_req->isoc_buffer) {
-        xen_be_unmap_grant_refs(xendev, usbback_req->isoc_buffer,
+        for (i = 0; i < usbback_req->nr_extra_segs; i++) {
+            ref[i] = usbback_req->req.seg[i + usbback_req->req.nr_buffer_segs].gref;
+        }
+        xen_be_unmap_grant_refs(xendev, usbback_req->isoc_buffer, ref,
                                 usbback_req->nr_extra_segs);
         usbback_req->isoc_buffer = NULL;
     }
@@ -832,11 +841,11 @@ static void usbback_disconnect(struct XenLegacyDevice *xendev)
     xen_pv_unbind_evtchn(xendev);
 
     if (usbif->urb_sring) {
-        xen_be_unmap_grant_ref(xendev, usbif->urb_sring);
+        xen_be_unmap_grant_ref(xendev, usbif->urb_sring, usbif->urb_ring_ref);
         usbif->urb_sring = NULL;
     }
     if (usbif->conn_sring) {
-        xen_be_unmap_grant_ref(xendev, usbif->conn_sring);
+        xen_be_unmap_grant_ref(xendev, usbif->conn_sring, usbif->conn_ring_ref);
         usbif->conn_sring = NULL;
     }
 
@@ -889,6 +898,8 @@ static int usbback_connect(struct XenLegacyDevice *xendev)
         return -1;
     }
 
+    usbif->urb_ring_ref = urb_ring_ref;
+    usbif->conn_ring_ref = conn_ring_ref;
     urb_sring = usbif->urb_sring;
     conn_sring = usbif->conn_sring;
     BACK_RING_INIT(&usbif->urb_ring, urb_sring, XC_PAGE_SIZE);