util: vfio-helpers: Factor out and fix processing of existing ram blocks

Factor it out into common code when a new notifier is registered, just
as done with the memory region notifier. This keeps logic about how to
process existing ram blocks at a central place.

Just like when adding a new ram block, we have to register the max_length.
Ram blocks are only "fake resized". All memory (max_length) is mapped.

Print the warning from inside qemu_vfio_ram_block_added().

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20210429112708.12291-2-david@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index 5a0a2d9..ccabed4 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -57,6 +57,7 @@
 void *qemu_ram_get_host_addr(RAMBlock *rb);
 ram_addr_t qemu_ram_get_offset(RAMBlock *rb);
 ram_addr_t qemu_ram_get_used_length(RAMBlock *rb);
+ram_addr_t qemu_ram_get_max_length(RAMBlock *rb);
 bool qemu_ram_is_shared(RAMBlock *rb);
 bool qemu_ram_is_uf_zeroable(RAMBlock *rb);
 void qemu_ram_set_uf_zeroable(RAMBlock *rb);