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>

3 files changed, 8 insertions, 7 deletions

diff --git a/include/hw/xen/xen-bus.h b/include/hw/xen/xen-bus.h
index 72d71d1eb7..5a90e79d53 100644
--- a/include/hw/xen/xen-bus.h
+++ b/include/hw/xen/xen-bus.h
@@ -102,7 +102,7 @@ void xen_device_set_max_grant_refs(XenDevice *xendev, unsigned int nr_refs,
 void *xen_device_map_grant_refs(XenDevice *xendev, uint32_t *refs,
                                 unsigned int nr_refs, int prot,
                                 Error **errp);
-void xen_device_unmap_grant_refs(XenDevice *xendev, void *map,
+void xen_device_unmap_grant_refs(XenDevice *xendev, void *map, uint32_t *refs,
                                  unsigned int nr_refs, Error **errp);
 
 typedef struct XenDeviceGrantCopySegment {
diff --git a/include/hw/xen/xen-legacy-backend.h b/include/hw/xen/xen-legacy-backend.h
index eaf79cd221..ab28583267 100644
--- a/include/hw/xen/xen-legacy-backend.h
+++ b/include/hw/xen/xen-legacy-backend.h
@@ -52,7 +52,7 @@ void xen_be_set_max_grant_refs(struct XenLegacyDevice *xendev,
 void *xen_be_map_grant_refs(struct XenLegacyDevice *xendev, uint32_t *refs,
                             unsigned int nr_refs, int prot);
 void xen_be_unmap_grant_refs(struct XenLegacyDevice *xendev, void *ptr,
-                             unsigned int nr_refs);
+                             uint32_t *refs, unsigned int nr_refs);
 
 int xen_be_copy_grant_refs(struct XenLegacyDevice *xendev,
                            bool to_domain, XenGrantCopySegment segs[],
@@ -65,9 +65,9 @@ static inline void *xen_be_map_grant_ref(struct XenLegacyDevice *xendev,
 }
 
 static inline void xen_be_unmap_grant_ref(struct XenLegacyDevice *xendev,
-                                          void *ptr)
+                                          void *ptr, uint32_t ref)
 {
-    return xen_be_unmap_grant_refs(xendev, ptr, 1);
+    return xen_be_unmap_grant_refs(xendev, ptr, &ref, 1);
 }
 
 /* actual backend drivers */
diff --git a/include/hw/xen/xen_backend_ops.h b/include/hw/xen/xen_backend_ops.h
index bb3333ab00..6f9d8e2c62 100644
--- a/include/hw/xen/xen_backend_ops.h
+++ b/include/hw/xen/xen_backend_ops.h
@@ -144,7 +144,8 @@ struct gnttab_backend_ops {
     int (*set_max_grants)(xengnttab_handle *xgt, uint32_t nr_grants);
     void *(*map_refs)(xengnttab_handle *xgt, uint32_t count, uint32_t domid,
                       uint32_t *refs, int prot);
-    int (*unmap)(xengnttab_handle *xgt, void *start_address, uint32_t count);
+    int (*unmap)(xengnttab_handle *xgt, void *start_address, uint32_t *refs,
+                 uint32_t count);
 };
 
 extern struct gnttab_backend_ops *xen_gnttab_ops;
@@ -204,13 +205,13 @@ static inline void *qemu_xen_gnttab_map_refs(xengnttab_handle *xgt,
 }
 
 static inline int qemu_xen_gnttab_unmap(xengnttab_handle *xgt,
-                                        void *start_address,
+                                        void *start_address, uint32_t *refs,
                                         uint32_t count)
 {
     if (!xen_gnttab_ops) {
         return -ENOSYS;
     }
-    return xen_gnttab_ops->unmap(xgt, start_address, count);
+    return xen_gnttab_ops->unmap(xgt, start_address, refs, count);
 }
 
 void setup_xen_backend_ops(void);