+
+ ``memory-backend='id'``
+ An alternative to legacy ``-mem-path`` and ``mem-prealloc`` options.
+ Allows to use a memory backend as main RAM.
+
+ For example:
+ ::
+ -object memory-backend-file,id=pc.ram,size=512M,mem-path=/hugetlbfs,prealloc=on,share=on
+ -machine memory-backend=pc.ram
+ -m 512M
+
+ Migration compatibility note:
+ a) as backend id one shall use value of 'default-ram-id', advertised by
+ machine type (available via ``query-machines`` QMP command), if migration
+ to/from old QEMU (<5.0) is expected.
+ b) for machine types 4.0 and older, user shall
+ use ``x-use-canonical-path-for-ramblock-id=off`` backend option
+ if migration to/from old QEMU (<5.0) is expected.
+ For example:
+ ::
+ -object memory-backend-ram,id=pc.ram,size=512M,x-use-canonical-path-for-ramblock-id=off
+ -machine memory-backend=pc.ram
+ -m 512M