memory-device: factor out get_memory_region() from pc-dimm

The memory region is necessary for plugging/unplugging a memory device.
The region size (via get_region_size()) is no longer sufficient, as
besides the alignment, also the region itself is required in order to
add it to the device memory region of the machine via
- memory_region_add_subregion
- memory_region_del_subregion

So, to factor out plugging/unplugging of memory devices from pc-dimm
code, we have to factor out access to the memory region first.

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20181005092024.14344-11-david@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/include/hw/mem/memory-device.h b/include/hw/mem/memory-device.h
index 898df3057d..659f38385c 100644
--- a/include/hw/mem/memory-device.h
+++ b/include/hw/mem/memory-device.h
@@ -38,6 +38,11 @@ typedef struct MemoryDeviceState {
  * mapped into guest physical address space at a certain address. The
  * address in guest physical memory can either be specified explicitly
  * or get assigned automatically.
+ *
+ * Conceptually, memory devices only span one memory region. If multiple
+ * successive memory regions are used, a covering memory region has to
+ * be provided. Scattered memory regions are not supported for single
+ * devices.
  */
 typedef struct MemoryDeviceClass {
     /* private */
@@ -69,6 +74,16 @@ typedef struct MemoryDeviceClass {
     uint64_t (*get_region_size)(const MemoryDeviceState *md, Error **errp);
 
     /*
+     * Return the memory region of the memory device.
+     *
+     * Called when (un)plugging the memory device, to (un)map the
+     * memory region in guest physical memory, but also to detect the
+     * required alignment during address assignment or when the size of the
+     * memory region is required.
+     */
+    MemoryRegion *(*get_memory_region)(MemoryDeviceState *md, Error **errp);
+
+    /*
      * Translate the memory device into #MemoryDeviceInfo.
      */
     void (*fill_device_info)(const MemoryDeviceState *md,