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, 8 insertions, 5 deletions

diff --git a/hw/net/xen_nic.c b/hw/net/xen_nic.c
index 7d92c2d022..166d03787d 100644
--- a/hw/net/xen_nic.c
+++ b/hw/net/xen_nic.c
@@ -181,7 +181,7 @@ static void net_tx_packets(struct XenNetDev *netdev)
                 qemu_send_packet(qemu_get_queue(netdev->nic),
                                  page + txreq.offset, txreq.size);
             }
-            xen_be_unmap_grant_ref(&netdev->xendev, page);
+            xen_be_unmap_grant_ref(&netdev->xendev, page, txreq.gref);
             net_tx_response(netdev, &txreq, NETIF_RSP_OKAY);
         }
         if (!netdev->tx_work) {
@@ -261,7 +261,7 @@ static ssize_t net_rx_packet(NetClientState *nc, const uint8_t *buf, size_t size
         return -1;
     }
     memcpy(page + NET_IP_ALIGN, buf, size);
-    xen_be_unmap_grant_ref(&netdev->xendev, page);
+    xen_be_unmap_grant_ref(&netdev->xendev, page, rxreq.gref);
     net_rx_response(netdev, &rxreq, NETIF_RSP_OKAY, NET_IP_ALIGN, size, 0);
 
     return size;
@@ -343,7 +343,8 @@ static int net_connect(struct XenLegacyDevice *xendev)
                                        netdev->rx_ring_ref,
                                        PROT_READ | PROT_WRITE);
     if (!netdev->rxs) {
-        xen_be_unmap_grant_ref(&netdev->xendev, netdev->txs);
+        xen_be_unmap_grant_ref(&netdev->xendev, netdev->txs,
+                               netdev->tx_ring_ref);
         netdev->txs = NULL;
         return -1;
     }
@@ -368,11 +369,13 @@ static void net_disconnect(struct XenLegacyDevice *xendev)
     xen_pv_unbind_evtchn(&netdev->xendev);
 
     if (netdev->txs) {
-        xen_be_unmap_grant_ref(&netdev->xendev, netdev->txs);
+        xen_be_unmap_grant_ref(&netdev->xendev, netdev->txs,
+                               netdev->tx_ring_ref);
         netdev->txs = NULL;
     }
     if (netdev->rxs) {
-        xen_be_unmap_grant_ref(&netdev->xendev, netdev->rxs);
+        xen_be_unmap_grant_ref(&netdev->xendev, netdev->rxs,
+                               netdev->rx_ring_ref);
         netdev->rxs = NULL;
     }
 }