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, 1 deletions

diff --git a/hw/xen/xen-operations.c b/hw/xen/xen-operations.c
index 2e74a28965..c5956d28c6 100644
--- a/hw/xen/xen-operations.c
+++ b/hw/xen/xen-operations.c
@@ -200,6 +200,13 @@ static xengnttab_handle *libxengnttab_backend_open(void)
     return xengnttab_open(NULL, 0);
 }
 
+static int libxengnttab_backend_unmap(xengnttab_handle *xgt,
+                                      void *start_address, uint32_t *refs,
+                                      uint32_t count)
+{
+    return xengnttab_unmap(xgt, start_address, count);
+}
+
 
 static struct gnttab_backend_ops libxengnttab_backend_ops = {
     .features = XEN_GNTTAB_OP_FEATURE_MAP_MULTIPLE,
@@ -208,7 +215,7 @@ static struct gnttab_backend_ops libxengnttab_backend_ops = {
     .grant_copy = libxengnttab_fallback_grant_copy,
     .set_max_grants = xengnttab_set_max_grants,
     .map_refs = xengnttab_map_domain_grant_refs,
-    .unmap = xengnttab_unmap,
+    .unmap = libxengnttab_backend_unmap,
 };
 
 void setup_xen_backend_ops(void)