xen: mapcache: Assert mapcache existance

Assert that the mapcache was created prior to being used.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

hw/xen/xen-mapcache.c

@@ -464,6 +464,8 @@ uint8_t *xen_map_cache(MemoryRegion *mr,
     MapCache *mc = mapcache;
     uint8_t *p;
 
+    assert(mapcache);
+
     if (grant) {
         mc = is_write ? mapcache_grants_rw : mapcache_grants_ro;
     }
@@ -530,6 +532,8 @@ ram_addr_t xen_ram_addr_from_mapcache(void *ptr)
 {
     ram_addr_t addr;
 
+    assert(mapcache);
+
     addr = xen_ram_addr_from_mapcache_single(mapcache, ptr);
     if (addr == RAM_ADDR_INVALID) {
         addr = xen_ram_addr_from_mapcache_single(mapcache_grants_ro, ptr);
@@ -652,6 +656,8 @@ static void xen_invalidate_map_cache_entry_bh(void *opaque)
 
 void coroutine_mixed_fn xen_invalidate_map_cache_entry(uint8_t *buffer)
 {
+    assert(mapcache);
+
     if (qemu_in_coroutine()) {
         XenMapCacheData data = {
             .co = qemu_coroutine_self(),
@@ -709,6 +715,8 @@ static void xen_invalidate_map_cache_single(MapCache *mc)
 
 void xen_invalidate_map_cache(void)
 {
+    assert(mapcache);
+
     /* Flush pending AIO before destroying the mapcache */
     bdrv_drain_all();
 
@@ -776,6 +784,8 @@ uint8_t *xen_replace_cache_entry(hwaddr old_phys_addr,
 {
     uint8_t *p;
 
+    assert(mapcache);
+
     mapcache_lock(mapcache);
     p = xen_replace_cache_entry_unlocked(mapcache, old_phys_addr,
                                          new_phys_addr, size);