Some SuperI/O devices such as the VIA south bridges or the PC87312 controller
are able to relocate their SuperI/O functions. Add a convenience function for
implementing this in the VIA south bridges.

This convenience function relies on previous simplifications in exec/ioport
which avoids some duplicate synchronization of I/O port base addresses. The
naming of the function is inspired by its memory_region_set_address() pendant.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
---
 docs/devel/migration.rst |  5 +++--
 include/exec/ioport.h    |  2 ++
 system/ioport.c          | 19 +++++++++++++++++++
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/docs/devel/migration.rst b/docs/devel/migration.rst
index ec55089b25..dc35a17461 100644
--- a/docs/devel/migration.rst
+++ b/docs/devel/migration.rst
@@ -452,10 +452,10 @@ data doesn't match the stored device data well; it allows an
 intermediate temporary structure to be populated with migration
 data and then transferred to the main structure.
 
-If you use memory API functions that update memory layout outside
+If you use memory or portio_list API functions that update memory layout outside
 initialization (i.e., in response to a guest action), this is a strong
 indication that you need to call these functions in a ``post_load`` callback.
-Examples of such memory API functions are:
+Examples of such API functions are:
 
   - memory_region_add_subregion()
   - memory_region_del_subregion()
@@ -464,6 +464,7 @@ Examples of such memory API functions are:
   - memory_region_set_enabled()
   - memory_region_set_address()
   - memory_region_set_alias_offset()
+  - portio_list_set_address()
 
 Iterative device migration
 --------------------------
diff --git a/include/exec/ioport.h b/include/exec/ioport.h
index 95f1dc30d0..96858e5ac3 100644
--- a/include/exec/ioport.h
+++ b/include/exec/ioport.h
@@ -54,6 +54,7 @@ typedef struct PortioList {
     const struct MemoryRegionPortio *ports;
     Object *owner;
     struct MemoryRegion *address_space;
+    uint32_t addr;
     unsigned nr;
     struct MemoryRegion **regions;
     void *opaque;
@@ -70,5 +71,6 @@ void portio_list_add(PortioList *piolist,
                      struct MemoryRegion *address_space,
                      uint32_t addr);
 void portio_list_del(PortioList *piolist);
+void portio_list_set_address(PortioList *piolist, uint32_t addr);
 
 #endif /* IOPORT_H */
diff --git a/system/ioport.c b/system/ioport.c
index a59e58b716..000e0ee1af 100644
--- a/system/ioport.c
+++ b/system/ioport.c
@@ -133,6 +133,7 @@ void portio_list_init(PortioList *piolist,
     piolist->nr = 0;
     piolist->regions = g_new0(MemoryRegion *, n);
     piolist->address_space = NULL;
+    piolist->addr = 0;
     piolist->opaque = opaque;
     piolist->owner = owner;
     piolist->name = name;
@@ -282,6 +283,7 @@ void portio_list_add(PortioList *piolist,
     unsigned int off_low, off_high, off_last, count;
 
     piolist->address_space = address_space;
+    piolist->addr = start;
 
     /* Handle the first entry specially.  */
     off_last = off_low = pio_start->offset;
@@ -322,6 +324,23 @@ void portio_list_del(PortioList *piolist)
     }
 }
 
+void portio_list_set_address(PortioList *piolist, uint32_t addr)
+{
+    MemoryRegionPortioList *mrpio;
+    unsigned i, j;
+
+    for (i = 0; i < piolist->nr; ++i) {
+        mrpio = container_of(piolist->regions[i], MemoryRegionPortioList, mr);
+        memory_region_set_address(&mrpio->mr,
+                                  mrpio->mr.addr - piolist->addr + addr);
+        for (j = 0; mrpio->ports[j].size; ++j) {
+            mrpio->ports[j].offset += addr - piolist->addr;
+        }
+    }
+
+    piolist->addr = addr;
+}
+
 static void memory_region_portio_list_finalize(Object *obj)
 {
     MemoryRegionPortioList *mrpio = MEMORY_REGION_PORTIO_LIST(obj);
-- 
2.43.0