memory-device: Add get_min_alignment() callback

Add a callback that can be used to express additional alignment
requirements (exceeding the ones from the memory region).

Will be used by virtio-mem to express special alignment requirements due
to manually configured, big block sizes (e.g., 1GB with an ordinary
memory-backend-ram). This avoids failing later when realizing, because
auto-detection wasn't able to assign a properly aligned address.

Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Wei Yang <richardw.yang@linux.intel.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20201008083029.9504-6-david@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/hw/mem/memory-device.h b/include/hw/mem/memory-device.h
index 30d7e99f52..48d2611fc5 100644
--- a/include/hw/mem/memory-device.h
+++ b/include/hw/mem/memory-device.h
@@ -89,6 +89,16 @@ struct MemoryDeviceClass {
     MemoryRegion *(*get_memory_region)(MemoryDeviceState *md, Error **errp);
 
     /*
+     * Optional: Return the desired minimum alignment of the device in guest
+     * physical address space. The final alignment is computed based on this
+     * alignment and the alignment requirements of the memory region.
+     *
+     * Called when plugging the memory device to detect the required alignment
+     * during address assignment.
+     */
+    uint64_t (*get_min_alignment)(const MemoryDeviceState *md);
+
+    /*
      * Translate the memory device into #MemoryDeviceInfo.
      */
     void (*fill_device_info)(const MemoryDeviceState *md,